I'm trying to figure out how I can use transformers for my Dart Server application. So far I've read the articles at https://www.dartlang.org/tools/pub/assets-and-transformers.html and https://www.dartlang.org/tools/pub/transformers/ and have used that information to write the following transformer.
import 'dart:async';
import 'package:barback/barback.dart';
class TestTransformer extends Transformer {
final BarbackSettings _settings;
TestTransformer.asPlugin(this._settings);
AssetId assetId;
Future<bool> isPrimary(AssetId id) {
assetId = id;
return new Future.value(id.toString().endsWith('.txt'));
}
apply(Transform transform) {
transform.primaryInput.readAsString().then((text) {
String output = text.toUpperCase;
print(output);
transform.addOutput(new Asset.fromString(assetId.addExtension('.upper'), output));
});
}
}
When I use pub run I see the transformer run, and the print line outputs as expected. What I'm missing is the *.txt.upper output file. I can't find such a file anywhere on my system. Where does this output end up, and how can I use it in my code? By use I mean being able to read the file with File.open() and, if the output is a Dart file, import it into another Dart file.
As far as I know are transformers for console/server applications not supported. When I run pub upgrade I also see after Precompiling dependencies that some transformers are loaded but this doesn't seem to process your source files.
Related
How do you read text from a file and write text to a file?
I've been learning about how to read and write text to and from a file. I found another question about reading from assets, but that is not the same. I will add my answer below from what I learned from the documentation.
Setup
Add the following plugin in pubspec.yaml:
dependencies:
path_provider: ^1.6.27
Update the version number to whatever is current.
And import it in your code.
import 'package:path_provider/path_provider.dart';
You also have to import dart:io to use the File class.
import 'dart:io';
Writing to a text file
_write(String text) async {
final Directory directory = await getApplicationDocumentsDirectory();
final File file = File('${directory.path}/my_file.txt');
await file.writeAsString(text);
}
Reading from a text file
Future<String> _read() async {
String text;
try {
final Directory directory = await getApplicationDocumentsDirectory();
final File file = File('${directory.path}/my_file.txt');
text = await file.readAsString();
} catch (e) {
print("Couldn't read file");
}
return text;
}
Notes
You can also get the path string with join(directory.path, 'my_file.txt') but you need to import 'package:path/path.dart'.
Flutter's Official Documentation of Reading and Writing Files
This works for iOS, Android, Linux and MacOS but not for web.
As additional info to #Suragch's answer, if you want to find the file you created, you can do as the images show:
And then inside that data folder, go again to a folder named data and search for your package, and then go to:
If you happen to create new files, in order to be able to see them, just right click and click Synchronize.
An another way to pull the file from the device is by using adb pull command. You can find the file path by debugging the code and then use adb pull command. adb is located in Android SDK -> platform-tools directory.
./adb pull /storage/emulated/0/Android/data/com.innovate.storage.storage_sample/files/sample.txt ~/Downloads
#Suragch 's answer is right. Except the version of path_provider that you want to use now is:
path_provider: ^2.0.9
I have a use-case for a pub transformer that isn't very typical, so I'm wondering if it's possible. I'd like to individually gzip every css, html, and javascript file produced during pub build. I have two questions about this:
Is it possible to transform compiled javascript?
Is it possible to configure the order that the transformer is run? Obviously, the gzip transformer would need to be the last transformer run.
In case you're wondering why I want to do this, I'm serving my app via S3 which doesn't support on-the-fly gzipping. I figure pub transformers would be the most appropriate place to do this.
You can specify order by the line position of the transformer:
transformers:
- $dart2js
- YourGzipTransformer
The above specifies that you want the dart2js transformer to run before YourGzipTransformer, thereby giving YourGzipTransformer access to the Javascript files generated by dart2js. If you swapped the order, or did not specify the order of the dart2js transformer, YourGzipTransformer would run before it and not have access to the compiled Javascript.
If you didn't care what order some transformers ran in, you could specify that too:
transformers:
- [$dart2js, SomeOtherTransformer]
- YourGzipTransformer
You can read more about this in the Assets and Transformers article.
Here's a basic transformer that will generate a gzipped version of every CSS, HTML, and Javascript file:
import 'dart:io';
import 'package:barback/barback.dart';
class GzipTransformer extends Transformer {
final BarbackSettings _settings;
GzipTransformer.asPlugin(this._settings);
#override
Future apply(Transform transform) {
return transform.primaryInput.readAsString().then((content) {
var id = transform.primaryInput.id;
var gzipId = id.changeExtension(id.extension +".gzip");
var gzippedContent = GZIP.encode(content.codeUnits);
transform.addOutput(new Asset.fromBytes(gzipId, gzippedContent));
});
}
String get allowedExtensions => ".js .css .html";
}
Barback package description:
An asset build system. Given a set of input files and a set of
transformations (think compilers, preprocessors and the like), will
automatically apply the appropriate transforms and generate output
files. When inputs are modified, automatically runs the transforms
that are affected. Runs transforms asynchronously and in parallel when
possible to maximize responsiveness.
Docs on assets and transformers say:
For pub serve, the transformers run when the dev server starts up and
whenever a source asset changes. The pub build command runs the
transformers once and then exits.
So I took this example:
// Copyright (c) 2014, the Dart project authors. Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.
import 'package:barback/barback.dart';
import 'package:markdown/markdown.dart';
import 'dart:async';
class ConvertMarkdown extends Transformer {
// A constructor named "asPlugin" is required. It can be empty, but
// it must be present. It is how pub determines that you want this
// class to be publicly available as a loadable transformer plugin.
ConvertMarkdown.asPlugin();
// Any markdown file with one of the following extensions is
// converted to HTML.
String get allowedExtensions => ".md .markdown .mdown";
Future apply(Transform transform) {
return transform.primaryInput.readAsString().then((content) {
// The extension of the output is changed to ".html".
var id = transform.primaryInput.id.changeExtension(".html");
String newContent = "<html><body>"
+ markdownToHtml(content)
+ "</body></html>";
transform.addOutput(new Asset.fromString(id, newContent));
});
}
}
It runs as expected with pub build, but does nothing with pub serve except printing:
Build completed successfully
every time I change any file (not only appropriate asset) in the directory.
After reading this I think that Dart has some problems with watching files(not only directories) on Windows platform.
It is true that pub serve runs transformers after each file modification. But compared to pub build it is not outputting the results to the build/ folder. pub serve is a development server, so you need to request you assets via HTTP, for example in a browser.
See the pub serve documentation for more details
Is there any way to access some of the attributes listed in a pubspec.yaml file in that files Dart application?
In particular, the version and description attributes may be quite useful to see in a version info dialog, or even a '--version' when using a console app. I haven't been able to find a way to access in the API. I'm not sure if Mirrors would have anything appropriate, but if a web app is compiled to JS, then I don't see the description anywhere in the output JS.
Thanks.
EDIT
feature request: https://code.google.com/p/dart/issues/detail?id=18769
FOR FLUTTER ONLY
Please use this new package package_info_plus from flutter community.
import 'package:package_info_plus/package_info_plus.dart';
PackageInfo packageInfo = await PackageInfo.fromPlatform();
String appName = packageInfo.appName;
String packageName = packageInfo.packageName;
String version = packageInfo.version;
String buildNumber = packageInfo.buildNumber;
BELOW SOLUTION IS DEPRICATED.
I know the OP wants to read YAML but for flutter dev's you guys can read the version and other info of the application using package_info.
This is the sample to fetch details from Android/iOS application.
import 'package:package_info/package_info.dart';
PackageInfo packageInfo = await PackageInfo.fromPlatform();
String appName = packageInfo.appName;
String packageName = packageInfo.packageName;
String version = packageInfo.version;
String buildNumber = packageInfo.buildNumber;
you can install the "dart_config" package and use this code to parse a pubspec.yaml file:
import 'package:dart_config/default_server.dart';
import 'dart:async';
void main() {
Future<Map> conf = loadConfig("../pubspec.yaml");
conf.then((Map config) {
print(config['name']);
print(config['description']);
print(config['version']);
print(config['author']);
print(config['homepage']);
print(config['dependencies']);
});
}
The output looks similar to this:
test_cli
A sample command-line application
0.0.1
Robert Hartung
URL
{dart_config: any}
EDIT
You can do it with the Yaml package itself:
*NOTE: this will not work on Flutter Web
import 'package:yaml/yaml.dart';
import 'dart:io'; // *** NOTE *** This will not work on Flutter Web
void main() {
File f = new File("../pubspec.yaml");
f.readAsString().then((String text) {
Map yaml = loadYaml(text);
print(yaml['name']);
print(yaml['description']);
print(yaml['version']);
print(yaml['author']);
print(yaml['homepage']);
print(yaml['dependencies']);
});
}
Regards Robert
None of the above answers worked for me, but here's a working solution for a Flutter app:
In your pubspec.yaml add the "pubspec.yaml" to assets:
assets:
- assets/
- pubspec.yaml
If you have a widget where you need to show the app version like this:
...
Container(
child: Text('Version: 1.0.0+1'),
),
...
Wrap your widget with a FutureBuilder like this:
import 'package:flutter/services.dart';
import 'package:yaml/yaml.dart';
...
FutureBuilder(
future: rootBundle.loadString("pubspec.yaml"),
builder: (context, snapshot) {
String version = "Unknown";
if (snapshot.hasData) {
var yaml = loadYaml(snapshot.data);
version = yaml["version"];
}
return Container(
child: Text(
'Version: $version'
),
);
}),
...
The services rootBundle property contains the resources that were packaged with the application when it was built.
If you want to show the version without the build number, you can split the string like so:
'Version: ${version.split("+")[0]}'
UPDATE: As mentioned by #wildsurfer, this approach has a potential security risk in web development because the pubspec.yaml is shared with the browser!
So assuming that this is for a dart cli application then the #Robert suggestion won't work.
dart_config isn't available for dart 2.x and your pubspec.yaml isn't going to be relative to your cwd except when you are in your development environment
So you need to get the pubspec.yaml relative to the libraries executable path.
This example uses the 'paths' package but it isn't required.
This can be obtained by:
import 'package:path/path.dart';
String pathToYaml = join(dirname(Platform.script.toFilePath()), '../pubspec.yaml');
You can now read the yaml:
import 'package:path/path.dart';
import 'package:yaml/yaml.dart';
String pathToYaml = join(dirname(Platform.script.toFilePath()), '../pubspec.yaml');
File f = new File(pathToYaml);
String yamlText = f.readAsStringSync();
Map yaml = loadYaml(yamlText);
print(yaml['name']);
print(yaml['description']);
print(yaml['version']);
print(yaml['author']);
print(yaml['homepage']);
print(yaml['dependencies']);
});
For Flutter only (Web, Android and IOS)... since October 2020
If you want your app working on Web, Android and IOS use "Package info_plus" instead.
How to Incorporate Automated Version Information into A Dart Command Line App
To update version information in your code without having to package a resource file to be parsed during run time, you can have the information hard coded into an automatically generated dart source file which gets compiled into your binary. The following example hard codes the version, name, and description information into the Map object "meta" in a meta.dart file. The meta.dart file is recreated and overwritten every time the test suite is run in development. To verify the source code has the correct version information, the app's code verifies the version and other meta information against the attributes in the pubspec.yaml file (but only when run as interpreted code in development). If there is a difference from pubspec.yaml, it throws an exception. Once compiled into a binary, it will skip that check as it won't find the pubspec.yaml file, so no error is thrown from the binary. Even if a pubspec.yaml file happens to be around and is found, it only throws an exception and does not create a "meta.dart" source file.
1. Create a MetaUpdate class and save it as "meta_update.dart":
import 'dart:io';
import 'package:yaml/yaml.dart';
import 'meta.dart';
class MetaUpdate {
String pathToYaml = "";
String metaDartFileContents = "";
MetaUpdate(this.pathToYaml);
void writeMetaDartFile(String metaDartFilePath) {
File metaDartFile = File(metaDartFilePath);
String metaDartFileContents = """
/// DO NOT EDIT THIS FILE EXCEPT TO ENTER INITIAL VERSION AND OTHER META INFO
/// THIS FILE IS AUTOMATICALLY OVER WRITTEN BY MetaUpdate
Map<String, String> meta = <String, String>{
"name": "${getPubSpec('name')}",
"description":
// ignore: lines_longer_than_80_chars
"${getPubSpec('description')}",
"version":"${getPubSpec('version')}",
};
""";
metaDartFile.writeAsStringSync(metaDartFileContents);
}
String getPubSpec(String pubSpecParam) {
File f = File(pathToYaml);
String yamlText = f.readAsStringSync();
// ignore: always_specify_types
Map yaml = loadYaml(yamlText);
return yaml[pubSpecParam];
}
void verifyLatestVersionFromPubSpec() {
try {
File f = File(pathToYaml);
//exit if no pubspec found so no warning in production
if (!f.existsSync()) return;
//compare meta.dart with pubspec meta and give warning if difference
if (meta.keys
.where((dynamic e) => (meta[e] != getPubSpec(e)))
.isNotEmpty) {
throw Exception(
"""Version number and other meta attributes in code are different from pubspec.yaml. Please check pubspec.yaml and then run test so that MetaUpdate can update meta information in code, then recompile""");
}
} on Exception {
rethrow;
}
}
}
2. Create a "meta.dart" file:
/// DO NOT EDIT THIS FILE EXCEPT TO ENTER INITIAL VERSION AND OTHER META INFO
/// THIS FILE IS AUTOMATICALLY OVER WRITTEN BY MetaUpdate
Map<String, String> meta = <String, String>{
"name": "Acme Transmogrifier",
"description":
"The best dart application ever.",
"version":"2021.09.001",
};
When you initially create the meta.dart file, copy your specific info from pubspec.yaml. This will later be overwritten each time your MetaUpdate.writeMetaDartFile() is run, changing the contents whenever the info in pubspec.yaml is changed.
3. Implement The Version Update In Your Test Code
Add the following in the first line of Main() in your test code (not the source of the main program, we don't want it to be compiled into the binary), changing the path to meta.dart as appropriate:
MetaUpdate("pubspec.yaml").writeMetaDartFile("lib/src/meta.dart");
4. Add A Meta Check To Your Main Code
Put this in your app's code so it is one of the first methods executed when your app is run - it will generate an exception if there is a difference between the attributes shown in the meta.dart and pubspec.yaml:
MetaUpdate("pubspec.yaml").verifyLatestVersionFromPubSpec();
5. Using
Make sure the Name, Version, and Description information in pubspec.yaml contains the latest information you want reflected in your code.
Import "meta.dart" and insert meta['name'], meta['version'], etc. where you need them to be shown (e.g., in --help or --version messages to be printed to the console).
As long as you run your tests before compiling your code the meta information will be accurately reflected in your code.
You can access pubspec.yaml properties with the official pubspec_parse package from the Dart team.
dart pub add pubspec_parse
import 'dart:io';
import 'package:pubspec_parse/pubspec_parse.dart';
final pubspec = File('pubspec.yaml').readAsStringSync();
final parsed = Pubspec.parse(pubspec);
You can then access typed properties on the parsed object.
You can find supported properties here: https://pub.dev/documentation/pubspec_parse/latest/pubspec_parse/Pubspec-class.html.
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