I am trying to build a library that currently has the following structure
lib
| src (contains some internal .dart files)
| | private_parts.dart
| strategies (contains sample strategies for applications)
| | scoring.dart
| | time.dart
| mylib.dart (the main library file to include)
My problem occurs when I try to write an application that uses the sample strategies. I get the error/warning The imported libraries 'scoring.dart' and 'time.dart' should not have the same name ''.
My main file looks something like this (placed in the web folder)
import 'package:mylib/mylib.dart';
import 'package:mylib/strategies/scoring.dart';
import 'package:mylib/strategies/time.dart';
main() {
game = new Engine(new StandardTime(), new StandardScoring());
}
How should I restructure the library to make it correct? What is best practice?
Your code doesn't show a library directive so I suppose more than one library has the library name 'NONE'.
Add a library directive at the top of your dart source file
library my_library.my_sublibrary; // <= this should differ for each library
In dart each source file is a library as long as you don't add
part of some_library
instead of the library directive. Adding no library or part of directive makes it implicitely a library without a name.
Related
I understand how to import one dart-polymer package into another package and use a component from the imported package.
There seems to be a difference in angular2-dart.
I created an angular2-dart component in package A and import it into package B.
The specific component I want to use is NameComponent.
In polymer I would simply do the following to used the imported component's markup
<name-component></name-component>
Doing something similar does not work in angular2-dart.
I have not been able to find information on importing a component from one dart package into another for angular2-dart.
A graphical summary of what I am trying to do is shown below - package B. The name-component is from package A.
Does anyone know how this is done?
EDIT 1
After making the suggested corrections I receive the following
"P:\Program Files\Dart\dev\dart-sdk\bin\pub.bat" serve web --port=57435
Loading source assets...
Loading angular2 and dart_to_js_script_rewriter transformers...
Serving epimss_ng2_app web on http://localhost:57435
[DirectiveProcessor on epimss_ng2_reg|lib/components.dart]:
ERROR: Invalid argument (url): "Could not read asset at uri asset:epimss_ng2_reg/lib/name_component.html"
[Warning from TemplateCompiler on epimss_ng2_app|lib/app_component.ng_meta.json]:
Could not find Directive entry for name: NameComponent
. Please be aware that Dart transformers have limited support for reusable, pre-defined lists of Directives (aka "directive aliases"). See https://goo.gl/d8XPt0 for details.
Build completed with 1 errors.
[web] GET Served 13 assets.
[web] GET packages/epimss_ng2_reg/components.dart => Could not find asset epimss_ng2_reg|lib/components.dart.
[web] GET Served 17 assets.
I am going to place the components directory directly on lib and see if it makes a difference.
My package is actually packages/epimss_ng2_reg/src/components.dart.
I can only think of 2 things you might be missing.
You need to add the component to directives
#Component(..., directives: const [NameComponent]) af the parent component.
You need to add the Angular2 transformer in pubspec.yaml of the component
transformers:
angular2
For Dart starters I'm working on a simple web which consists of less than 10 classes. I'm totally confused as for how to organized them in files, folders (and packages? and libraries?).
Currently I have
web/
img/
*.png
styles/
main.css
index.html
main.dart
*.dart
All but one Dart file contain a single class. Imports are done through import 'a.dart'; (e.g. in b.dart).
This is obviously wrong because the Dart Editor complains about
The imported libraries 'c.dart' and 'd.dart' should not have the same
name ''
I went through the respective sections in pub documentation and read about possible app structures in the Polymer docs. I also looked at the structure of the pop_pop_win sample application that comes with Dart. It's all a bit overwhelming because there are so many variations, options and combinations.
If I were you, I would create libraries and imports like so:
awesomeLibrary.dart
library awesome;
part 'foo.dart';
part 'bar.dart';
foo.dart
part of awesome;
class Foo
{
static function Baz() {}
}
bar.dart
part of awesome;
class Bar
{
...
}
main.dart
import 'awesomeLibrary.dart';
void main()
{
Foo.Baz(); // Imported library function
}
** This question is edited and cleaned up some **
I have two projects and I want to use code from one in the other; I seem to be having trouble putting the code in the right directory structure to make the import statements work.
Both projects are created and managed exclusively from the Dart Editor on a Mac, if that makes any differences.
Project Directory Structures
Project 1: a command line app which contains the code I want to share in the following directory structure:
/dart/command_line_app
/lib
shared_library.dart
/bin
command_line_app.dart
Project 2: a web app which wants to import the code in shared_libary.dart
/dart/web_application
/packages
/web
web_application.dart
In the file shared_libary.dart, I declare it to be a library can create a simple class that provides output when instantiated:
library shared_library;
class ShareMe
{
ShareMe()
{
print("Hello, ShareMe");
}
}
This compiles, and works inside the command_line project: command_line_app.dart has the following:
import 'package:command_line_app/shared_library.dart';
void main() {
ShareMe shareMe = new ShareMe();
print("Hello, World!");
}
This imports the code runs, printing both "Hello Share Me," and Hello World.
THE PROBLEM
I want to instantiate the ShareMe class inside web_application.dart. I'd thought I could do that by putting in the same import statement I put in my command_line code:
import 'package:command_line_app/shared_library.dart';
But, when I put the same import into the web_appliation, it gets the error
Target of URI does not exist 'package:command_line_app/shared_library.dart'
Other Things I've Tried
I was certain I'd solved the problem when I cntrl-Clicked properties on Web_application and selected Project References.
It brings up a window allowing me to select command_line_app with a check box, but when I do, I get an error:
Could not set the project description for 'web_application' because the project description file (.project) is out of sync with the file system.
Whatever that means.
When I cntrl-click the underlined error and try Quick Fix it offers me "resolve dependencies" which sounds promising, but after a few seconds, it comes back and informs me that
Pub get failed, [1] Resolving dependencies... (15.3s)
Could not find package command_line_app at https://pub.dartlang.org.
Depended on by:
- web_application 0.0.0
I hope this is clear-er and gives a better insight into both what I'm trying to do and what I'm missing.
EDIT
you need to add
dependencies:
command_line_app:
path: ../command_line_app
to your dependencies in web_application/pubspec.yaml.
EDIT END
When you want to make code reusable in different packages, you should put that code into the lib directory of that package and import it using import 'package:mypackage/myfile.dart';.
Another problem you may face is, that browser applications can't import packages that have a dart:io dependency. If you want to reuse code between command line and browser applications you should move them into the lib directory of another package my_shared_code where you put only code that doesn't depend on dart:io (for example some entity classes) and import this code from both app packages (browser and command line).
Suppose I have this:
benchmark.dart:
library benchmark;
benchmark() {...}
app.dart:
import 'benchmark.dart'; // functions from this lib are now accessible in this file
export 'benchmark.dart'; // does this make them accessible in all files imported below?
import 'model.dart';
void main() {
doSomething();
}
model.dart
doSomething() {
benchmark(); // => Error, no such method, unless
// I import 'benchmark.dart' above in this file!
}
Is this the right behavior? How do I make benchmark accessible without importing the lib in model.dart?
You have to make the imports in every library you want to use other libraries.
What you might do is to join several files to one library using part 'model.dart'; (parent file) and part of app; (linked file).
Then the types and functions imported in the parent file are available in all files of this library.
I know you can use the library, import and even #import, but which is correct?
I have got two files, MainClass.dart and Library.Dart, and I want to add a reference to Library.dart in MainClass.dart. How can I do that?
Firstly let me just preface this by saying please do not use the hash symbol before import or library or anything else. This is an old syntax that is being deprecated. So we no longer want to use #import('...') The correct syntax is:
import 'some_file.dart';
That said, there are two different things we can do to access different dart source files within our current file. The first is to import the file. We use this such as in your case when you want to bring a different library into the current file (or more accurately current library).
Usually if your files are in the same directory, or a sub directory of the current one we would import them like this:
import 'lib/library.dart';
However If you are using the pub package layout you can also use some special short-cut references as well to import files (particularly from other packages you've imported). I highly suggest reading the documents on the pub site, as most applications and libraries are designed with this in mind. It also has suggestions on best naming conventions such as filenames in all lower case, and using underscore for spaces, and directory layouts.
The other important thing to know about bringing a dart file into another file, is that we can use the part and part of directives. This used to be called #source but was changed (with the removal of the hash sign) to reduce confusion. The part directive is used when we want to write a single library which spans multiple files. Say for instance you have an Awesome Library, which is starting to get a little large for a single file. We will create the main file of the library (not to be confused with the main method). This file will usually have the same name as the library itself.
// awesome_library.dart
library awesome_library;
import 'dart:math';
import '...';
// this injects all the content of secret_file.dart
// into this file right here almost as if it was
// here in the first place.
part 'src/secret_file.dart';
// The rest of our file here
// ...
The part directive basically takes everything from our src/secret_file.dart and inserts it into that part of the file. This allows us to split our huge Awesome Library into multiple smaller files that are easier to maintain. While not specifically required, it is helpful to use the part of directive in our secret_file.dart to help the editor know that it is "part of" the library.
// secret_file.dart
part of awesome_library;
// ... Rest of our secret_file code below.
Note that when using a part file like this, the part(s) (that is everything that is not the main file of the library) cannot import or use library declarations themselves. They import whatever is imported into the the main file, but they cannot add any additional imports.
For more information about library see this link.
Importing your own created libraries:
You will be importing the filename.dart and not the name of your library.
So if the name of your library is: myLib and it is saved in the file: someDartFile.dart you will have to
import 'someDartFile.dart';
If you have on Windows a library at: K:\SomeDir\someFile.dart you will need to write:
import '/K:/SomeDir/someFile.dart';
example:
import 'LibraryFile.dart'; //importing myLib
void main(){
//a class from myLib in the LibraryFile.dart file
var some = new SomeClassFromMyLibrary();
}
myLib in LibraryFile.dart:
library myLibrary;
import 'dart:math';
class SomeClassFromMyLibrary{
String _str = "this is some private String only to myLibrary";
String pubStr = "created instances of this class can access";
}
Here a full example.
//TestLib.dart
import 'LibFile.dart'; //SomeLibrary
void main() {
print("Hello, World!");
LibFile l = new LibFile();
print(l.publicString);//public
print(l.getPrivateString);//private
print(l.getMagicNumber); //42
}
//LibFile.dart
library SomeLibrary;
part 'LibFile2.dart';
class LibFile {
String _privateString = "private";
String publicString = "public";
String get getPrivateString => _privateString;
int get getMagicNumber => new LibFile2().number;
}
//LibFile2.dart
part of SomeLibrary;
class LibFile2 {
int number = 42;
}
Although i am answering very late, but the answer may help new developer.
Always use pubspec.yaml file in your dart package(application/library).
once you run pub get command it will add your local library in the dependencies list in .packages file.
Consider i have following project structure.
To refer to the content of greeting.dart in my main.dart file i should add the library as below
import 'package:my_project_name/greeting.dart'
Once imported we can use the content of greeting.dart file in our main.dart file.
Note: we have not used the actual path as you can see 'lib' directory is missing.
First make sure that's the name which you have mentioned in pubspec.yaml and the file you want to import are sharing the exact same name
example:
pubspec.yaml
name: flutter_wordpress_app
description: flutter wordpress app
...
....
// dirOne/dirTwo/greeting.dart
class FavArticleBloc {
// Your code goes here
}
import 'package:flutter_wordpress_app/dirOne/dirTwo/greeting.dart'
void main(){
var some = new FavArticleBloc();
}
But
in the main.dartyou don't need to specify
import 'package:flutter_wordpress_app
just do like below
import 'dirOne/dirTwo/greeting.dart