I've been learning Ruby on Rails for quite some time now and have built several toy applications. I've taken many classes/courses (i.e., Hartl, Code School, Udemy, etc.). Now I'm working on a pet project that is fairly complex - many models and relationships.
Here's my question: How do I go about thinking about a complex application in terms of models and relationships? It seems to me there should be some visual way to model all of this, but I haven't seen any discussion of such modeling in any of the classes I've taken. Sure, there's the very simple diagrams in the Rails Guides, but how do I extend this to something more complex? Or, am I making this too complicated? Do I just start coding models and relationships and see where it takes me? It seems this ad hoc approach could easily paint me into a corner where I'll have to start over from scratch if I paint myself into a corner, so to speak.
Are there tools or blog posts that can help me?
(Note: I've also posted this question at Reddit.Com/r/Rails at https://www.reddit.com/r/rails/comments/7c9zbf/how_to_think_about_rails_web_application/)
It sounds like what you're after is a schema designer. I'll link one at the bottom of this post. A schema designer will allow you to visualize all the relationships in your application, and see how one model connects to another. They're really helpful in writing complex DB queries. I've attached an example of a fairly simple design just to give you an idea what they do.You can also add all the columns a model has in the design, I just usually use it more for relationships.
http://ondras.zarovi.cz/sql/demo/
Purely based on my experience/opinion...
You'll end up changing your database design a couple of times as you build your app.
I would start with a whiteboard, then consider using a schema designer as #aram mentioned.
After you see the big picture, just start with the relationships that what you need for today's features. You can keep referring to the original design, so you can see the bigger picture, but you don't want to overbloat your architecture before you need to because it will change.
After you write some code and build those relationships, you can spot check yourself using the rails-erd gem to programmatically generate your app's schema.
I have recently been tasked to look into Workflow Foundation. The actual goal would be to implement a system in which the end users can define custom workflows in the deployed application (and of course, use them). Personally I have never used WF before (and reading around here on SO people are very doubtful about it - so am I reading those questions/answers), and I am having a hard time finding my way around it given the sparse learning resources available.
Anyway, there are some questions, for example, this, which mention something they call dynamic or user-defined workflows. They point out that WF makes it possible to "rehost" the designer, so that end-users can define their own new workflows after the application is deployed (without developer intervention (?), this is the part I am not really sure about).
I have been told by fellow employees that this way we could implement an application in which once this feature is implemented we would no longer have to keep modifying the application every time a new workflow is to be implemented. However, they also pointed out that they just "heard it", they don't have firsthand experience themselves either.
I have been looking around for samples online but the best thing I could find was a number guess app - barely more than a simple hello world. So not much that would point me to the right direction of how this user-defined workflow feature actually works and how it can be used, what its limitations are etc.
My primary concern is this: it is alright that one can define custom workflows but no workflow is worth a penny without the possibility of actually inputting data throughout the process. For example, even if the only thing I need to do is to register a customer in a complaint management system, I would need the customer's name, contact, etc. If the end user should be able to define any workflow the given toolset makes possible then of course there needs to be a way to provide the workflow consumers with a way of inputting data through forms. If the workflow can be of pretty much any nature then so needs to be the data - otherwise if we need to implement the UIs ourselves then this "end-user throws together a workflow" feature is kind of useless because they would still end up at us requiring to implement a form or some sort of data input for the individual steps.
So I guess that there should be a way of defining the "shape" of the data that needs to be filled at any given user interaction phase of the workflow which I can investigate and dynamically generate forms based on the data. So for example, if I found that the required data was made up of a name and a date of birth, then I would need to render a textbox and a datepicker on the page.
What I couldn't really figure out from the Q&As here and elsewhere is whether this is even possible. Can I define and then later "query" the structure of the data to be passed to the workflow at any point? If so, how? If not, how should this user-defined workflow feature even be used, what is it good for?
To clarify it a little, I could imagine something as specifying a complex type, which would be the view model (input model) in a regular MVC app, and then I could reflect over it, get the properties and render input fields based on that.
Windows Workflow Foundation is about machine workflows, not business workflows. True, it is the foundational tool set Microsoft created for building their business workflow products. But out of the box WWF does not have the components you need to quickly and easily build business workflows. If you want to send an email in a workflow, you have to write that from scratch. Just about anything you can think of doing from a business point of view you have to write from scratch.
If you want to easily create business workflows using Microsoft products check out the workflow stuff in SharePoint. It is the easiest of the Microsoft products to work with (in my experience.) If that does not meet your needs there are other products like BizTalk.
K2 is another company with a business workflow product that uses WWF as their base to more easily build business workflows, the older K2 products actually create web pages automatically to collect the data from the user.
WWF is very low level, arguably it lost traction after they re-wrote the whole thing in 4.0. While not publically stated by Microsoft, my personal opinion is Service Fabric (from Microsoft) achieves the goals WWF originally tried to solve which was a "more robust programming environment."
I'm starting out with Ruby on Rails and I know of a few stuff already, but I was wondering if there was a "right" way of going about developing a project. Right now, I would create my models first using [script/generate model MyModel] then modifying them until I feel they are complete enough. Then I'd go for [script/generate scaffold MyModel] so I don't need to do as much coding for the views. Lastly I modify the views and add more models then scaffold some more for other features I might need.
Would there be a better way of doing this? Especially in the context of working with a team in developing a project? Thanks!
I'm sure everyone has their own workflow, but I think a typical one is this:
Specify the "domain" your project. This probably sounds silly, but before you get started you should really think about what exactly your website is going to offer. It doesn't need to be specific down to the last detail, but should have an idea so that you can perform the next step...
Design your database schema. I usually just plan this out on paper. There's a real art to creating a normalized database. Think of everything that needs to be "permanent" in your app, because it will have to be in the database and accounted for, with as little duplication as possible.
After this I usually do as you say: create my models (and migration scripts along the way). The main thing you want to get down in your models first is the associations with other models.
The next part depends on how comfortable you are as a developer in Rails. A lot of people enjoy the test driven development approach (TDD), and will write Unit tests (Rails provides excellent facilities for writing these, and rake tasks to run them). However, since you're just learning, you may want to write your tests after you implement your model business logic.
The road after this is pretty much up to you. You can work on your views/controllers/models as you need to. That's one of the beauties of Rails and agile development, you don't need a lot of boiler plate code to get started.
I'm probably weird in this, but I usually design my front page and get some basic CSS going, as I find I am more productive if my results are semi-nice looking.
I would probably avoid generating scaffolds though...I think you'll learn a lot more about the framework and spend less time removing unwanted code if you generate the individual pieces themselves.
In the context of developing with a team, things will probably be different. If you have a lot of complex business logic, some people may spend most of their time writing model code, while people more on the design side will be implementing view code. But you will have to meet in the middle of course, which will get easier as your project grows and becomes more modular. Just remember to use a version control system! Subversion if you want something easy to use and learn, Git if you're up for a challenge.
That is a broad question, and I appreciate no short/dumb asnwers like: "Oh that is the model job, this quest is retarded (period)"
PROBLEM Where I work at people created a system over 2 years for managing the manufacture process over demand in the most simplified still broad as possible, involving selling, buying, assemble, The system is coded over Ruby On Rails.
The app has been changed lots of times and the result is a mess on callbacks (some are called several times), 200+ models, and fat controllers: Total bad.
The QUESTION is, if there is a gem, or pattern designed to handle Rails large app logic? The logic whould be able to fully talk to models (whose only concern would be data format handling and validation)
What I EXPECT is to reduce complexity from various controllers, and hard to track callbacks into files with the responsibility to handle a business operation logic. In some cases there is the need to wait for a response, in others, only validation of the input is enough and a bg process would take place.
ie:
--> Sell some products (need to wait the operation to finish)
1. Set a View able to get the products input
2. Controller gets the product list inputed by employee and call the logic
Logic::ExecuteWithResponse('sell', 'products', :prods => #product_list_with_qtt, :when => #date, :employee => current_user() )
This Logic would handle buying order, assemble order, machine schedule, warehouse reservation, and others.
Have in mind that a callback on SalesOrder is not enough, since it depends on where it is called (no field for that), depends on the class of the user, among other stuff not visible for the model, or in some cases it would take long for the model to process.
The inherent complexity of the business object and logic will need to be tackled with, understood, and internalized (or at least documented well) for the team. That will not go away. The recommendation I have is to grab all the logic peppered throughout the "fat" controllers and move them into either the domain objects, application services (service layer), or simply transaction scripts (see Martin Fowler's "Patterns of Enterprise Application Architecture").
Ideally all the business logic embedded in the labyrinth of callbacks can be refactored into components described above to promote understanding. This gets rid of all the incidental complexity built up over time on the controllers. But even after getting rid of all that, I suspect a certain level of inherent complexity will remain in the problem domain.
The idea of Service Layer is to incorporate high level logic which is not associated with certain model in a good way. If you develop enterprise like system with multiple services integrated and have number of data sources you should better look to Domain-Driven Design (DDD) by Eric Evans. Surely, Fowler's Enterprise patterns book is good in this case too.
Also look at DataMapper(2, the first one was similar to ActiveRecord). It has better design approach for such type of systems and have less limitation (on conceptual level) than ActiveRecord in Rails.
Truly say, that's because of dynamic nature of Ruby people so long tackling conceptual problems of ActiveRecord and try to fit it enterprise needs, IMHO.
Some people have done some work out there on service layers and callbacks Pat Maddox (especially callbacks) is one, Jay Fields (his very early works around the rails presenter pattern later to be replaced with a service layer like pattern) is another. I must admit I like the idea of adding a extra layer. To me, business logic just doesn't belong in models and models should be decoupled in complex projects. I also like the idea of an extra layer over callbacks, for me callbacks become too complex as there numbers increase
This is far from full blown DDD and at the moment I don't know how DDD would work in Rails, however ,I am sure it could and I am sure someone is working on it out there right now. For my projects, at the moment, it would be a bit of a overkill to implement, however, I would consider adding a service layer.
At my company we're about to build a new site using ASP.NET MVC. My boss (marketing guy) would like to know some more about the technology so I've tried to find a really good, simple and pedagogical presentation of the MVC concept without any luck. Most of them require quite a lot of basic knowledge in programming.
Any suggestions for a good video, slides or other?
Craig Strong has a pretty nice article about MVC in general and how to explain its benefits to business. Check it out here: Updated link.
Define MVC in layman’s terms
Remember you’re technically minded and close to the code. MVC to you
is as clear as day, but saying to the business ‘Model, View,
Contoller’ could give them the impression that you are suffering from
some form tourette syndrome. MVC won’t mean much to the business even
after you define them in relation to the code. To get the business to
understand why this is the answer and least of all what it is, can be
more of a task than expected in my experience. Even some fellow
developers have difficulty understanding this on occasion.
To get the listener to understand what MVC is and why it works what I
have tried in the pass is to apply MVC to a different industries where
the listeners have had more involvement. An example that has worked
for me in the past in a comparison to the property or even the
vehicles. Most people have had dealing’s with builders, carpenters,
plumbers, electricians or have watched the flood of property shows on
the TV. This experience is a good platform to use and to explain why
separation such as MVC works. I know you’re probably thinking that
won’t work as it’s not the same as in software, but remember you’re
not trying to train the business to become developers or have an in
depth understanding of MVC, simply explaining to them that separation
in production is required and that’s what an MVC structure offers.
To give an example of how you could describe this I have very briefly
explained how separation works in property. Keep in mind this is
focused on using the system not developing which could be a completely
different angle of explanation.
View
The view in MVC is the presentation layer. This is what the end user
of a product will see and interact with. A system can have multiple
views of all different types ranging from command line output to
rendered HTML. The view doesn’t consist of business logic in most
clear designs. The interface is fit for purpose and is the area of
interaction. Therefore you could simply output HTML for consumers to
interact with or output SOAP/XML for businesses to interact with. Both
use the same business logic behind the system otherwise known as the
models and controllers.
In the world of property you could think of the view as the interior
of a property or the outer layer of a property that the inhabitants
interact with. The interior can be customised for purpose and the same
property can have many different types of tenants. For example a
property of a particular design could contain residential dwellings.
The same internal space could easily be used as office space, where
although in the same property has a different purpose. However the
property structure is the same. Therefore the environment in which the
users interact does not interfere with the structure of the building.
Controllers
The controller is where the magic happens and defines the business
application logic. This could be where the user has sent a response
from the view, then this response is used to process the internal
workings of the request and processes the response back to the user.
Taking a typical response where a user has requested to buy a book.
The controller has the user id, payment details, shipping address and
item choice. These elements are then processed through the business
logic to complete a purchase. The data is passed through the system
into the model layer and eventually after the entire request satisfies
the business definitions, the order is constructed and the user
receives their item.
If we compare this to a property, we could compare the ordering of a
book online to turning on a light switch. A tenant will flick the
switch to on just like ordering a book. The switch itself is an
element in the view layer which sends the request to the controller
just like clicking a checkout button on a web site. The business logic
in this case is what the electrician installed and are embedded within
the property designs. The switch is flicked, which completes the
circuit. Electricity runs through all the wires including the fuse box
straight through to the light bulb. Just like the user receiving a
book, in this case the tenant receives light. The whole process behind
the scenes involving the electricity cabling is not visible to the the
tenant. They simply interact with the switch within the space and from
there the controller handles the request.
Models
The models in MVC are the bottom most layer and handle the core logic
of the system. In most cases this could be seen as the layer that
interacts with the data source. In systems using MVC, the controller
will pass information to the model in order to store and retrieve
data. Following on from the example above controller definition, this
is where the order details are stored. Additional data such as stock
levels, physical location of product of the book amongst many things
are all stored here. If that was the last book in stock ordered, the
next request for this item may check if it’s available and disallow
the order as the item is no longer available.
Sticking with our example of turning on a light switch, this level in
our structure could be the electricity supply. When the tenant flicks
the switch, the internal circuit must request electricity to power the
request which is similar when the user requested data from the
database, as in data is needed to process a request. If the dwelling
isn’t connected to an electric supply, it cannot complete the process.
Business benefits from using MVC
After you get the message across explaining what MVC is, you will then
have to see what benefits can be obtained from it. I’m not going to go
into a huge amount of detail here are I’m sure you can apply benefits
more accurately which are directly related to you actual situation. To
list just some of the common benefits of an MVC based system here are
a few examples:
Different skill levels can work on different system levels. For example designers can work on the interface (View) with very little
development knowledge and developers can work on the business logic
(Controller) with very little concern for the design level. Then they
simply integrate together on completion.
As a result of the above separation projects can be managed easier and quicker. The designer can start the interfaces before the
developer and vice versa. This development process can be parallel as
opposed to being sequential therefore reducing development time.
Easy to have multiple view types using the same business logic.
Clear route through the system. You clearly know where there different levels of the system are. With a clear route of the system,
logic can be shared and improved. This has added security benefits as
you clearly know the permitted route from the data to the user and can
have clear security checks along the route.
Each layer is responsible for itself. (Relates to point 1) This means that you can have clean file structure which can be maintained
and managed much easier and quicker than a tightly couple system where
you may have lots of duplicate logic.
Having a clear structure means development will be more transparent which should result in reduced development time,
maintenance problems and release cycles if applied properly.
M-V-C Think of it as:
"Order Details (including Customer & Employee info)", "HTML/ASP Form (to display the OrderDetails)" and "Order details service class (having methods to SaveOrderDetails, GetOrderDetails etc.).
The Model (Data Class e.g. OrderDetails)
The data you want to Display
The Controller (Service class)
Knows about the Model (Order Details)
Has methods to manage the Model
And as such can be unit tested Its Single Responsibility is to manage the OrderDetails CRUD operations.
It knows NOTHING about the View
The View (ASP Page)
Displays the Model (OrderDetail's ViewData).
It has to know about the Model's structure so it can correctly display the data to the users on screen.
The View's structure (style, layout, HTML etc., locale) can be changed at anytime without it changing anything in the application's functionality.
And as such, many Views can display the same Model in many different ways.
In multi-tenant web applications, Customer specific Views can be stored in a database table and displayed based on Customer information
You have to explain the benefits of ASP.NET MVC, not the features
You have control over your URLs -- that means SEO for the site will be better -- that means your site will be higher in google
The code is cleaner, which means that it's easier to change, which means that you can add features faster
etc.
How do you save money, make money, reduce risk? That's what your boss wants to know.
Imagine a control room in a factory, the model is the machine itself, the monitoring equipment is the view and the instrument panel is the controller. You could have several different control rooms for the same machine and changes in the controls in one control room would reflect on the monitors in all control rooms.
The point is that you should only model once and then view or control however is most convenient.
The model is the data access layer, which can just be a wrapper for a few simple queries to an ORM that manages the data entity relationships itself. It handles communication to the data source, retrieves data and usually organizes it into objects defined in your application.
The views are just html files with bits of html and css with some templating engine (smarty, mako, etc) code to display the data passed to it the way you want.
The controller puts it all together. Requests made to your page will be routed to a controller (class) and an action (method) within the controller. Just like any other application, the action will do what's requested of it, but it's still part of the controller.
So, the controller uses the model to query data (users, content, etc), then passes the data to a view to be rendered and displayed the way you want.
I wouldn't try to explain the technology to him, I'd try to explain what the MVC architectural principle is all about.
MVC was designed to separate concerns. Plain and simple. Explain to him that when you build anything that what you're building can be classified in two different categories: what the business need is (the domain), and everything else.
MVC separates the Domain from the everything else by introducing layers to separate out the concerns. M is for Model, which is your domain. V is for View, which is the visible part to him, what he sees. C is for Controller, the part that controls what is going on in between the Domain and the View.
The marketing guy would just be interested in the "V" part, the View. Depending on how you design things, the View would just be basic HTML/CSS "templates" that the marketing person could modify. Technically without breaking anything.
Ideally the Model (database) and Controller (logic) shouldn't care if the View (presentation) is XML, HTML, text, etc. The marketing person shouldn't care what the Model and Controller do, except for requesting additional functionality.
Going further with the "ideal", you should technically be able to replace ASP with PHP, Java, Ruby, etc as the Controller without touching the Model or View.
You can very easily do this, that is if you understand marking speak. I dont but I imagine it would go something like this...
This should be use. MVC (if done right) will allow you to decouple the UI from the data (model) and control of the UI (controler). This will allow the UI to be more flexible which will in turn allow to better market it self faster.
To a marketing guy, perhaps the best way to explain the reason for ASP.Net MVC is the ability to broaden your product's reach.
By using MVC, the code is already separated in a fashion that will let you more easily build an interface that feels natural on a desktop, and then the different interface that caters to a general mobile device user, and a still-slightly-different interface that caters to an iPhone user, without risking the backend code getting out of sync and introducing subtle and company-harming bugs. And, if there's a smart client desktop app that could be a product... it, too, can rest on the same codebase.
The Model is "how things work inside the box". The Controller is "what you can touch on the outside of the box" and the view is "what comes out of the box"...
The most important thing for your marketing guy is money, budget, TCO ...
When you don't use MVC you usually mix design, application logic etc. alltogether.
Programmer then must know html design, programming etc... That could mean you need powerful professional to do it all.
if you use MVC, everything is divided into "separate parts". Html coder can prepare html layer, programmer only works with application logic etc...
MVC brings better granularity and everybody can focus on what he or she can do the best!
Listen, for example xhtml validity and css cleanliness is so hard that there is a lot of people who focuses only on this while lot of browsers and platforms compatibility on mind.
Usually one person is NOT the best asp.net programmer, xhtml coder in one ;-)
This is a pretty simple one
http://en.wikipedia.org/wiki/Model-view-controller#Pattern_description
The best way I can thing of is that the model is the data representation, the view is the presentation to the user and the controller is what collects user interaction that changes the model.
The important word in the title of the manager in this case is "marketing." He is a Marketing manager. The concerns one has as a marketing manager have to do with strategy and tactics. These two are not the same thing. Strategy is the big picture word that embraces among other things how a company conceptually addresses customer needs and how the company differentiates itself from its competition. Strategy is typically not what software can portray to a user. Tactics, on the other hand, are the direct methods or approaches that a company takes in winning the business of the customer. Tactics tend to change far more frequently than strategies, and it is likely that the marketing manager, when he asks what advantage MVC may give him, is really asking, "How rapidly can you change whatever it is that you create into something that conforms to new realities in the way we have to deal with customers." In other words, how quickly can you change an offer of "buy 1 and get 1 free" into "buy 2 on Friday and get 1 on the following Tuesday if it is raining in Albany."
Marketing management is about results measured in dollars and cents, not finery and nuanced explanations that are littered with conceptual words lacking any real specificity. Everything a programmer may say might make sense to himself, but a marketing manager needs to know the real likelihood of rapid response to changing customer perceptions or rapid implementation to a different approach to selling to the same customers. He needs to know if it will cost more than an existing method because if he sells $1 million more in product while spending $1.25 million in software development, he will probably lose his job.
So, in short, he is looking for flexibility and cost-effectiveness. He needs software that be adapted to changing conditions quickly, just as he changes his pitch first one way and then another to a difficult-to-persuade prospective customer, and he needs to know that he won't have to be liable for a huge price tag for that flexibility.
Frankly, I don't think that you would be able to deliver on such promises if they were made because in spite of all the advantages of MVC from a development point of view, we are still talking about software here, and as we all know, software is a rigid, demanding taskmaster that takes it own sweet time to mature to the point of trustworthiness and to be rid of its bugs. We as programmers are always in search of the holy grail of software reusability, and while we flail about trying one thing and then another (MVC, MVP, MVVM, and whatever else someone may conceive), the rest of the world is simply asking for something that works. So the best of luck to you. I hope you are able to win your case.