I am trying to follow the steps to change the Gridworld appearance according to this. I've already imported source code for my gridworld jar file; ie. I can go and look at Bug.class or Gridpanel.class if I wanted to. However, I can't edit these files to produce the results that that pdf suggests. How do I do this? Did I import the source code incorrectly?
I don't think you can edit an external resource like gridworld.jar. You are going to need to create 4 new packages:
actor
grid
gui
world
Then copy the class files from gridworld.jar packages into your corresponding ones. Now you can edit the files. Make sure you include any miscellaneous files that might also be in the gridworld.jar packages, their important.
With your own packages you no longer need the gridworld.jar external resource, and there is a difference in your import statements. Instead of
import gridworld.actor.Actor;
Do this:
import actor.Actor;
Note: You will need to change all of the import statements in the new package classes to reference the other new packages. I believe that there were also some errors, not project breaking, but I just added suppressors.
Related
In my dart project projectxyz, I have a dart class declared in in myclass.dart. In main.dart, Android Studio gives two ways, both work, but I did not understand what are the pros and cons of each method:
import 'myclass.dart';
or:
import 'package:projectxyz/myclass.dart';
What is the difference in these two approaches?
That depends on how the main file itself is invoked (and where it's located).
I'll assume the main.dart library is inside the lib/ directory, because otherwise you wouldn't have the two options for importing myclass.dart.
If you invoke the main file with a file: URI, then the relative import of myclass.dart will also be imported with a file: URI. Since Dart uses the import URI to distinguish different libraries, if someone else imports myclass.dart using a package: URI, then it will be treated as two different libraries introducing different classes with the same name.
It used to be that running dart lib/main.dart would treat that as a file: URI. The Dart parser has gotten smarter about that, and now it recognizes that an entry point library in a lib/ directory should have been a package: URI, and replaces the entry point URI with package:projectxyz/main.dart.
After that, it makes no difference whether you use myclass.dart or package:projectxyz/myclass.dart.
Really, there is no difference between the two. Saying import 'myclass.dart' is high-level sugar for import 'package:projectxyz/myclass.dart';.
On the other hand, import 'myclass.dart' is easier to read and understand, and generally looks better. It also decreases confusion as to where exactly your code is being imported from, as anybody who reads this statement knows to look for the file elsewhere in your project. Because of this, you should try to use this form wherever possible.
Yes, I read dart import and part of directives in same file
I have this structure:
lib/
src/
one/
SomeClass.dart
one.dart
mylib.dart
main.dart
I'm trying to achieve this behavior:
All public and hidden variables are fully accessible inside library.
All public variables from library are accessible to main.dart.
There is a problem. For some weird reason I can't use any directive with 'part of'. So I can't use this in the one.dart:
part of mylib;
import 'SomeClass.dart';
//somecode
So I either need to move class definition from SomeClass.dart to one.dart (and that will make code less readable and mixed up) or I need to move 'import' in the mylib.dart.
library mylib;
import 'SomeClass.dart';
part ..
I don't like either of the options. In the second case I will need to parse all modules then and move import/exports. Which will definitely break something.
It may sound weird but the project will build from various modules automatically. And one/ is one of them.
This app design is bad, I know. But either I need to find a better way or just make all variables public and don't bother.
Default to defining one type per file, not using part, and importing only the files you need. This covers the majority of use cases.
Now, let's say you have two types that are commonly used together - for example, a Thing and a ThingException that gets thrown when Thing does bad things. Importing both of these files everywhere is tedious, so you have three options with their own tradeoffs:
Declare both types in the same file.
Declare each type in its own file, and have the 'primary' file export the other. So, thing.dart exports thing_exception.dart. Importing thing.dart gives the importing file access to both.
Declare each type in its own file, and have the other file be a 'part of' the primary file. So, thing_exception.dart declares that it is 'part of' thing.dart. Importing thing.dart gives the importing file access to both files.
For this simple type and its exception, your best bet is to use option 1. When the amount of code grows or the two types diverge in visibility, this option becomes less attractive. This puts options 2 and 3 are on the table.
When you have separate files, option 2 is often a better approach than options 3 because you maintain some flexibility - you could only import thing_exception.dart and not thing.dart. If you use option 3, you can't do this - you either import all of the parts or none of them. This is the error you are seeing when trying to do a part and import in the same file.
Option 3 becomes valuable when you the code is in the two files is highly dependent on one another and they need the ability to access private members of each other. This is less common.
When you have a bunch of files like this together, it becomes a 'library' in the more traditional sense. You declare a main library file (your my lib.dart file) that exports files:
export 'public.dart';
export 'other_public.dart';
The bin script imports the library as a whole, but it can't see anything that isn't explicitly exported from my_lib.dart.
import 'package:mylib/mylib.dart';
Here's an example of a smallish package that uses all three of these options together for a good reference.
I think you will have better luck using import, and export with show. (Use of part of is now discouraged.)
Answers to this question may help you: When to use part/part of versus import/export in Dart?
Also the Creating library packages documentation: https://www.dartlang.org/guides/libraries/create-library-packages
Many of the samples I have seen for angular2 have the following import statement:
import {bind} from 'angular2/di';
I am working in VS Code (with TypeScript) and it complains about not being able to find the angular2/di module.
However I do see a bind function defined in angular2/angular2.d.ts. If I change the import statement to the following, then the error goes away.
import {bind} from 'angular2/angular2';
Is the question in the title off-base and I am making some erroneous assumption?
If not, why do many samples reference one module to import the bind function from, yet I seem to be able to get it from a different module?
Most likely because you looked at versions from older alphas. Look at the angular2.ts file. Everything is exported from it. Also note that the d.ts is going to contain everything to resolve types in your IDE and at compilation time. What import does is actually importing the .js files.
Create a sample web application using the Web UI (web_ui) library, e.g., mylib
open mylib.dart, make it a library:
library mylib;
import 'dart:html';
import 'package:web_ui/web_ui.dart';
part 'xclickcounter.dart';
...
open xclickcounter.dart, remove imports and insert:
part of mylib;
web/out/mylib.dart and web/out/xclickcounter.dart get messed up:
The included part ''xclickcounter.dart'' must have a part-of directive
Classes can only mixin other classes
Mixin can only be applied to class
... more errors follow
What am I doing wrong? Please help :(
Edit: if I don't edit generated sample code, wdc will generate code that falls into separate libraries:
web/out/xclickcounter.dart => x_click_counter
web/out/mylib.dart => mylib_html
Does it mean that if we use web_ui we should not create our own libraries and wdc will do this for us automatically?
Update: if I don't use any library name, similar to what generated sample code does, and only rely on the library names generated by xdc in web/out/... files, I still run into trouble when importing my two components into a 3rd file. Dart Editor will produce the following warning:
The imported libraries 'compa.dart' and 'compb.dart'
should not have the same name
The workaround is to name your libraries based on what xdc produces in web/out/... files, that is:
compa.dart => x-comp-a
compb.dart => x-comp-b
After explicitly placing components into libraries like these the Dart Editor warning disappears.
When I create a 'Web Application' with DartEditor in Windows8, it gives me this hierarchy
ClientView/
packages/
pubspec.lock
pubspec.yaml
web/
packages/
clientview.css
clientview.dart
clientview.dart.js
clientview.dart.js.deps
clientview.dart.js.map
clientview.html
I then add the lib/ file:
web/
...
lib/
src/
canvas.dart
i_drawable.dart
node.dart
client_canvas.dart
...
client_canvas.dart file
library client_view;
import 'dart:html';
import 'package:meta/meta.dart';
// Interface
part 'src/i_drawable.dart';
// Class
part 'src/canvas.dart';
part 'src/node.dart';
In each of the files included after the 'part' keyword, I've added this line:
part of client_view;
But it seems that none of the classes can be accessed by the other dart code
class Canvas implements IDrawable // no such type 'IDrawable'
abstract class Node implements IDrawable // no such type 'IDrawable'
class CustomNode extends Node // no such type 'Node' (if try to create a custom node)
I guess it's the way pubs and library are organized that I've not understood yet.
So what I tried to do is to create a library, inside the same project, I'd like to import that library inside the clientview.dart file that is called by the clientview.html file.
Your help would be greatly appreciated!
Since you're using relative imports, and everything appears to be part of the same library, I see no obvious reason for the errors. Maybe you can share some more details.
You should probably reorganize your source tree to be more inline with Pub standards though. web/ and lib/ should both be top level directories, otherwise you won't be able to do package: imports of your own libraries. This is one reason why it's recommended that web/ only contain entry points (scripts with a main() method) and everything else should be in lib/.
Also, I would try to use part very sparingly. I find it much better to define almost every file as a library and just import them. It makes dependencies for each file much more clear and allows consumers to only import the interfaces, and not the implementations. export makes it possible to build a library that exposes the definitions of another.
Finally, a style nit: Dart isn't C# and we don't use that ugly 'I' prefix on our interfaces :-) Just name your interface Drawable.