How do I do this console.error(foo); in Dart?
The print() method gets quite close, but it's not exactly what I want. I want to have the notification of an error and the icon along with the stack trace.
It's actually very simple to do in Dart:
import 'dart:html';
main() {
window.console.error('Something bad occurred');
}
Related
Consider following dart code:
main.dart
import 'module.dart';
main() {
foo();
}
module.dart
foo() {
print('foo');
}
bar() {
print('bar');
}
I expect bar to be eliminated from the final build by dart compiler with tree-shaking since it's statically analyzable that the function was not used in main.
I tried the method answered in related S/O question.
Using devtools by running dart run --observe main.dart, I still see bar was included.
How can I know whether bar was eliminated from the final build or not?
Alternatively, I want someone with an understanding of dart compiler to convince me whether the function was eliminated or not, so I don't need to worry about checking it myself.
import 'dart:collection';
void main(){
PriorityQueue<double> p;
}
This code wont check, as Dart analyser cannot find PriorityQueue in collection. I believe that PriorityQueue is in there, so is there something wrong with my analyser? It does sometimes produce false errors, do I need to reset the cache? (I've tried, but maybe I didn't do it right)
PriorityQueue is not in dart:collection, it is in a different "collection" unit, the package:collection package, which you'll need to import as a dependency.
Like this
in pubspec.yaml:
dependencies:
collection: ^1.14.13
Then import 'package:collection/collection.dart'; in your code.
I'm writing a Dart console app for the first time and I've searched the Internet everywhere and can't find the proper answer.
In Python, the function raw_input(); takes user input from stdin in a similar way to Dart's stdin.readLineSync();, however raw_input(); takes a parameter: If I do something like raw_input(">>");, the CLI does something like:
>> _
In Dart, however, I cannot find a way to do something similar with stdin.readLineSync();, it simply outputs:
_
Is there a simple way for a new Dart user to accomplish this? Thank you for your time.
This might do what you want:
import 'dart:io';
main() {
stdout.write('>> ');
var result = stdin.readLineSync();
print(result);
}
write does not automatically add a newline.
A simpler way is to use the DCli package and its ask function:
var response = ask('>>');
print(response);
The ask function provides a number of other options that help capturing data from the cli such as the functions 'confirm' and 'menu'.
https://onepub.dev/packages/dcli
I am creating a scientific calc app in DART . i dont knw how to use trignometric functions like sine , cosine . i used "math.sin()" , but it throws an exception "NO top-level getter math.get declared " how to solve it ? thanks in advance
To use trigonometric functions in Dart, import the dart:math library. For example:
import 'dart:math';
main() {
print(sin(pi));
}
If you want, you can import with a prefix to avoid namespace collisions:
import 'dart:math' as Math;
main() {
print(Math.sin(Math.pi));
}
I'm trying to use Isolates in Dart. The tutorials from dartlang.org seem to use the function spawnFunction. But that does not seem to work for me. And I cant find any docs about this.
import 'dart:isolate';
void doThing() {
print('Hello!');
}
main() {
spawnFunction(doThing);
}
.
Unhandled exception:
No top-level method 'spawnFunction' declared.
The docs from api.dartlang.org mention Isolate.spawn but I get an error saying there is no static method spawn declared.
Did I miss something? A link to appropriate docs (if any) would be appreciated.
Thanks!
Isolate.spawn is indeed the new way of creating isolates. Your example would need to be rewritten as:
import 'dart:isolate';
void doThing(_) {
print("Hello!");
}
main() {
Isolate.spawn(doThing, null);
}
See https://groups.google.com/a/dartlang.org/forum/#!topic/misc/EVUMkZXFXtY for the breaking change announcement.