In nodejs I simply use path
import path from "path";
path.resolve(__dirname, '../', './test.txt');
Is there any way to use in dart ?
import 'package:path/path.dart' as path;
void main(List<String> args) {
final relative = 'example/example.dart';
final absolute = path.normalize(path.absolute(relative));
print(absolute);
final dir = path.dirname(absolute);
print(dir);
final absolute2 =
path.normalize(path.absolute(path.join(dir, '../', './test.txt')));
print(absolute2);
}
Output (in my case):
E:\prj\dart_test\example\example.dart
E:\prj\dart_test\example
E:\prj\dart_test\test.txt
P.S.
I prefer to use normalize but this is matter of taste.
You probably want to use File.absolute.path/Directory.absolute.path.
Related
Let's say we want to create a simple dart file, that just declares a class containing consts. E.g.
class StringNames {
static const String helloWorld = 'Hello World';
}
But rather than write this manually, we want to generate this file programmatically. We want a program that will create this file for us.
We could write such a program in dart itself, e.g.
import 'dart:io';
void main() {
final f1 = 'file1.dart';
File(f1).writeAsString('class stringNames {\nstatic const String helloWorld = \'HelloWorld\';\n}');
}
Naturally this feels wrong. Is there a better way to achieve this?
You could use multi-line string as described here in the Dart language tour:
https://dart.dev/guides/language/language-tour#strings
So your example becomes like this, which is much more readable:
import 'dart:io';
void main() {
final f1 = 'file1.dart';
File(f1).writeAsString('''
class StringNames {
static const String helloWorld = 'Hello World';
}
''');
}
You can also use this and insert values from variables inside the string like this:
import 'dart:io';
void main() {
final f1 = 'file1.dart';
final someValue = 42;
File(f1).writeAsString('''
class StringNames {
static const String helloWorld = 'Hello World';
static const int someValue = $someValue;
}
''');
}
I am new to DART, and i would like to know is there any way to choose random characters from am given string in DART.
Any built-in functions available?
Thanks
Well, you can use the Random class from dart:math to make your own function:
import 'dart:math';
void main() {
print(getRandomLetter('Hello World'));
}
final _rnd = Random();
String getRandomLetter(String input) => input[_rnd.nextInt(input.length)];
I want to delete file in Directory.
It is created like so.
final Directory extDir = await getTemporaryDirectory();
final String dirPath = '${extDir.path}/video';
await new Directory(dirPath).create(recursive: true);
final String filePath = '$dirPath/${timestamp()}.mp4';
I want to delete this specific path so that app won't heavy.
How can I do this?
Does anyone have an idea?
You don't need to move to the directory. You pass the path to the Directory constructor:
import 'dart:io';
void main() {
final dir = Directory(dirPath);
dir.deleteSync(recursive: true);
}
I am using Flutter to load an "asset" into a File so that a native application can access it.
This is how I load the asset:
final dbBytes = await rootBundle.load('assets/file');
This returns an instance of ByteData.
How can I write this to a dart.io.File instance?
ByteData is an abstraction for:
A fixed-length, random-access sequence of bytes that also provides
random and unaligned access to the fixed-width integers and floating
point numbers represented by those bytes.
As Gunter mentioned in the comments, you can use File.writeAsBytes. It does require a bit of API work to get from ByteData to a List<int>, however.
import 'dart:async';
import 'dart:io';
import 'dart:typed_data';
Future<void> writeToFile(ByteData data, String path) {
final buffer = data.buffer;
return new File(path).writeAsBytes(
buffer.asUint8List(data.offsetInBytes, data.lengthInBytes));
}
I've also filed an issue to make the docs on Flutter more clear for this use case.
you need to have path_provider package installed, then
This should work :
import 'dart:async';
import 'dart:io';
import 'dart:typed_data';
import 'package:path_provider/path_provider.dart';
final dbBytes = await rootBundle.load('assets/file'); // <= your ByteData
//=======================
Future<File> writeToFile(ByteData data) async {
final buffer = data.buffer;
Directory tempDir = await getTemporaryDirectory();
String tempPath = tempDir.path;
var filePath = tempPath + '/file_01.tmp'; // file_01.tmp is dump file, can be anything
return new File(filePath).writeAsBytes(
buffer.asUint8List(data.offsetInBytes, data.lengthInBytes));
}
//======================
to get your file :
var file;
try {
file = await writeToFile(dbBytes); // <= returns File
} catch(e) {
// catch errors here
}
Hope this helps,
Thank you.
to search flutter ByteData to List<int> then found here, but not fully answer my question:
how to convert ByteData to List<int> ?
after self investigate, solution is:
use .cast<int>()
ByteData audioByteData = await rootBundle.load(audioAssetsFullPath);
Uint8List audioUint8List = audioByteData.buffer.asUint8List(audioByteData.offsetInBytes, audioByteData.lengthInBytes);
List<int> audioListInt = audioUint8List.cast<int>();
or 2. use .map
ByteData audioByteData = await rootBundle.load(audioAssetsFullPath);
Uint8List audioUint8List = audioByteData.buffer.asUint8List(audioByteData.offsetInBytes, audioByteData.lengthInBytes);
List<int> audioListInt = audioUint8List.map((eachUint8) => eachUint8.toInt()).toList();
For those looking to write bytes (aka Uint8List) instead of ByteData please note that ByteData is a wrapper for Uint8List.
From /runtime/lib/typed_data.patch:
#patch
class ByteData implements TypedData {
#patch
#pragma("vm:entry-point")
factory ByteData(int length) {
final list = new Uint8List(length) as _TypedList;
_rangeCheck(list.lengthInBytes, 0, length);
return new _ByteDataView(list, 0, length);
}
#patch
class Uint8List {
#patch
#pragma("vm:exact-result-type", _Uint8List)
factory Uint8List(int length) native "TypedData_Uint8Array_new";
}
If you are using the latter type you can use the answer provided by Rami and modify the return as follow:
import 'dart:async';
import 'dart:io';
import 'dart:typed_data';
import 'package:path_provider/path_provider.dart';
Future<File> writeToFile(Uint8List data) async {
(...)
return new File(filePath).writeAsBytes(data);
}
I have a list of models that I need to create a mini reflective system.
I analyzed the Serializable package and understood how to create one generated file per file, however, I couldn't find how can I create one file for a bulk of files.
So, how to dynamically generate one file, using source_gen, for a list of files?
Example:
Files
user.dart
category.dart
Generated:
info.dart (containg information from user.dart and category.dart)
Found out how to do it with the help of people in Gitter.
You must have one file, even if empty, to call the generator. In my example, it is lib/batch.dart.
source_gen: ^0.5.8
Here is the working code:
The tool/build.dart
import 'package:build_runner/build_runner.dart';
import 'package:raoni_global/phase.dart';
main() async {
PhaseGroup pg = new PhaseGroup()
..addPhase(batchModelablePhase(const ['lib/batch.dart']));
await build(pg,
deleteFilesByDefault: true);
}
The phase:
batchModelablePhase([Iterable<String> globs =
const ['bin/**.dart', 'web/**.dart', 'lib/**.dart']]) {
return new Phase()
..addAction(
new GeneratorBuilder(const
[const BatchGenerator()], isStandalone: true
),
new InputSet(new PackageGraph.forThisPackage().root.name, globs));
}
The generator:
import 'dart:async';
import 'package:analyzer/dart/element/element.dart';
import 'package:build/build.dart';
import 'package:source_gen/source_gen.dart';
import 'package:glob/glob.dart';
import 'package:build_runner/build_runner.dart';
class BatchGenerator extends Generator {
final String path;
const BatchGenerator({this.path: 'lib/models/*.dart'});
#override
Future<String> generate(Element element, BuildStep buildStep) async {
// this makes sure we parse one time only
if (element is! LibraryElement)
return null;
String libraryName = 'raoni_global', filePath = 'lib/src/model.dart';
String className = 'Modelable';
// find the files at the path designed
var l = buildStep.findAssets(new Glob(path));
// get the type of annotation that we will use to search classes
var resolver = await buildStep.resolver;
var assetWithAnnotationClass = new AssetId(libraryName, filePath);
var annotationLibrary = resolver.getLibrary(assetWithAnnotationClass);
var exposed = annotationLibrary.getType(className).type;
// the caller library' name
String libName = new PackageGraph.forThisPackage().root.name;
await Future.forEach(l.toList(), (AssetId aid) async {
LibraryElement lib;
try {
lib = resolver.getLibrary(aid);
} catch (e) {}
if (lib != null && Utils.isNotEmpty(lib.name)) {
// all objects within the file
lib.units.forEach((CompilationUnitElement unit) {
// only the types, not methods
unit.types.forEach((ClassElement el) {
// only the ones annotated
if (el.metadata.any((ElementAnnotation ea) =>
ea.computeConstantValue().type == exposed)) {
// use it
}
});
});
}
});
return '''
$libName
''';
}
}
It seems what you want is what this issue is about How to generate one output from many inputs (aggregate builder)?
[Günter]'s answer helped me somewhat.
Buried in that thread is another thread which links to a good example of an aggregating builder:
1https://github.com/matanlurey/build/blob/147083da9b6a6c70c46eb910a3e046239a2a0a6e/docs/writing_an_aggregate_builder.md
The gist is this:
import 'package:build/build.dart';
import 'package:glob/glob.dart';
class AggregatingBuilder implements Builder {
/// Glob of all input files
static final inputFiles = new Glob('lib/**');
#override
Map<String, List<String>> get buildExtensions {
/// '$lib$' is a synthetic input that is used to
/// force the builder to build only once.
return const {'\$lib$': const ['all_files.txt']};
}
#override
Future<void> build(BuildStep buildStep) async {
/// Do some operation on the files
final files = <String>[];
await for (final input in buildStep.findAssets(inputFiles)) {
files.add(input.path);
}
String fileContent = files.join('\n');
/// Write to the file
final outputFile = AssetId(buildStep.inputId.package,'lib/all_files.txt');
return buildStep.writeAsString(outputFile, fileContent);
}
}