I need to call a method from my action object inside the JSP, something like:
var currentStatus = ${getCurrentStatus()};
I cannot call an attribute, and I tried following this answer (How to call an action method using OGNL) and it didn't work.
There are a variety of ways to call methods (on actions, on other objects, or static methods from classes) from OGNL.
In this case, however, I don't see any issue with using a normal accessor. Note that the JavaBean convention is almost (completely?) about naming. A getter named getCurrentStatus(), accessed simply in OGNL via currentStatus, can contain whatever code you want.
This could include the DB access you mention in your question, etc.
Related
I'm creating a wrapper class for an API because my application will need to call it with different credentials at different times. I started off passing the wrapper a method and arguments and then doing (basically) this when calling it
call
set_credentials
TheAPI::Thing.send(method, args)
ensure
reset_credentials_to_default
end
HOWEVER, I realized that a challenge here is if I need to chain methods; this way I can only call one at a time; so for example I wouldn't be able to to TheAPI::Thing.find(id).delete. (At least, not without re-calling the credentials setter, which is undesirable since I have to fetch a token).
Is there a way using ruby to collect the methods/args being chained onto an object? Or would I simply have to pass in some ugly ordered set of things?
EDIT: Surely activerecord's query builder does something like this, collecting the chained methods before returning, and then after they're all collected, ensuring that as a final step the query is built, called, and returned?
the way to do this is to define a proxy object and to pass that around instead of the actual thing.
In the object itself, hold a reference to the Thing and override method_missing: http://ruby-doc.org/core-2.1.0/BasicObject.html#method-i-method_missing
In the method missing do the thing you are doing today. In a nutshell this is what ActiveRecord is doing.
As far as chaining things, I don't believe it would be a problem as methods that can be chained usually return references to self. When you call the 2nd method in the chain, you actually have done the work for the first one and have an object that has the 2nd method in the chain. The only trick you need to pay attention to is that you want to return a reference to the proxy class that encapsulates the thing instead of the actual return of the thing if you want the chaining to succeed.
Give it a shot and ping me if you run into trouble and I can spin up a fully working example.
I have a method like this.
def process(file){
if(file != null && !file.empty){
anotherMethod(file.inputStream);
}
}
If I call this method from Java, what type of object do I need to pass into this method? I tried File,ZipFile but they don't have empty method.
It's impossible to say for definite without seeing more context (where is this method usually called from the Grails application, for example), but a possible candidate would be MultipartFile, or rather one of its concrete implementations such as MockMultipartFile. The empty and inputStream properties that the groovy code is accessing correspond to the isEmpty() and getInputStream() bean-style accessor methods of this interface.
The normal purpose of this type is to handle multipart/form-data file uploads - it's what you get when you call request.getFile('fieldName') in a controller.
Suppose I want my class to do things on attribute access. I can of course do that in setters and getters:
class Foo {
set bar (v) {
// do stuff
}
}
However, if I want to attach the same behavior to multiple attributes, I'd have to explicitly define the same setters and getters for every one of them. (The use case I have in mind is an observable, i.e. a class that knows when its attributes are being changed).
What I'd like to do is something like:
class Foo {
var bar = new AttributeWithAccessBehavior();
}
Python does this with descriptors - what is the closest thing in Dart?
AFAIK there isn't anything with getter/setter syntax that you can reuse.
You could assign a function to a field, that you can access using call notation (), but you have to be careful to call the function instead of overriding the field assignment.
A similar but more powerful alternative are classes that can emulate functions (see https://www.dartlang.org/articles/emulating-functions/)
A class that has a call method can be used like a method.
This is similar to assigned functions mentioned above but in addition you can store state information.
If you implement actual getter/setter you can of course delegate to whatever you want, but that is obviously not what you are looking for.
For the use case you mentioned, there is the observe package.
I have no idea how exactly it solves the problem, but it works quite well.
I've found properties corresponding to each action named like this: MVC.<Controller>.<Action>Params, they contain parameter names for each action. What are they for and how they can be used?
There were some edge scenarios where it was interesting to pass the parameter name as a constant. I can't instantly recall what that person was doing, but I could see this being useful is calls to AddRouteValue. In the end, it's all about never to have to use a literal string that refers to a C# object, whether it's a class, method, or param.
I have a base Controller ApplicationController that needs to grab the URL Host and do some processing before the child controllers are fired. Since controller constructors are fired before RequestContext is initialized I have to override Initialize method to do my processing.
ApplicationController:
Protected Overrides Sub Initialize(ByVal requestContext As System.Web.Routing.RequestContext)
MyBase.Initialize(requestContext)
Dim host as String
host = Request.Url.Host.ToString
End Sub
What is the logic behind having Controller Constructors fire before the Initialize method?
Also what are the rules to what should be placed in the Initialize Method.
Assuming that constructors are the first instance method ever to be fired in a .NET class, that shouldn't come as a surprise and is not really something MVC specific. It's more how the .NET framework works.
The MVC framework needs to first instantiate a controller and then initialize it => it calls the constructor first. And because performing lots of code that could potentially might throw exceptions, etc... is not always best to be put in a constructor => the presence of the Initialize method. As far as this method is concerned I must admit that I have written lots of ASP.NET MVC code and never had to use it. Action filters always seemed like a better alternative.
So to answer your question:
Also what are the rules to what should be placed in the Initialize Method.
I've never ever put any code and never ever need to override this method. I've always preferred using action filters because this way I am no longer in the obligation of deriving from a common base controller (not that this is a problem).
Sometimes, maybe you would want your request to initialize your variables, so in this case you should use the Initialize method.
For example, if you want to initialize some variables in a different way when the request is local or not, etc.