How to shorten code when I do a variable assignment in a condition in Dart?

Question

Here's the ugly long code:

var i;
if(true)
  i = 1;
else
  i = 0;

When I try this:

var i = (true ? 0 : 1);

it doesn't work resulting in an error on the following line. I guess I was a bit inattentive reading Dart's syntax specs, so can anybody show me the right way?

What's the error you are getting? I just get a 'Dead code' warning. — Günter Zöchbauer
– Günter Zöchbauer, Commented Jan 16, 2014 at 7:58
That's not directly an answer and maybe just an error on SO, but the two snippets produce different results. var i = (true ? 1 : 0) would be the equivalent, you switched the "if" and "else" there. — MarioP
– MarioP, Commented Jan 16, 2014 at 9:20

Günter Zöchbauer · Accepted Answer · 2014-01-16 08:04:25Z

12

This looks perfectly fine from a syntax point of view. You can omit the parentheses.

I get a warning 'Dead code' at '1' with your example because of 'true'.
The Darteditor shows you a hint that you wrote code that may contain a bug because he knows your expression can never evaluate to 1 because of the hardcoded 'true'.

void main(List<String> args) {
    var b = true;
    var i = b ? 0 : 1;
}

doesn't produce a warning.

edited Jan 16, 2014 at 8:04

answered Jan 16, 2014 at 7:57

Günter Zöchbauer

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5 Comments

mezoni Over a year ago

What about check to null? bool b; var i = b ? 0 : 1; type 'Null' is not a subtype of type 'bool' of 'boolean expression'.

Günter Zöchbauer Over a year ago

This is a runtime error due to a not initialized variable. That has nothing to do with syntax and IMHO not with the question.

mezoni Over a year ago

Question is "How to shorten code when I do a variable assignment in a condition in Dart?". Your answer to main question not take that if shorten code in your manner you can get runtime error. var i = (b == null ? false : true) ? 0 : 1;

Günter Zöchbauer Over a year ago

Good point. @snitko 's example is a bit too simplified due to his true literal.

orion3 Over a year ago

Ok, thanks. For some reason it just didn't work in my case. I'll check my code again.

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