In Dart is there a quick way to convert int to double?

Very simple issue. I have the useless class:

class Useless{
double field;
Useless(this.field);
}

I then commit the mortal sin and call new Useless(0); In checked mode (which is how I run my tests) that blows up, because 'int' is not a subtype of type 'double'.

Now, it works if I use new Useless(0.0) , but honestly I spend a lot of time correcting my tests putting .0s everywhere and I feel pretty dumb doing that.

As a temporary measure I rewrote the constructor as:

    class Useless{
double field;
Useless(num input){
field = input.toDouble();
}
}

But that's ugly and I am afraid slow if called often. Is there a better way to do this?

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There's no better way to do this than the options you included :(

I get bitten by this lots too, for some reason I don't get any warnings in the editor and it just fails at runtime; mighty annoying :(

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Simply toDouble()

Example:

int intVar = 5;
double doubleVar = intVar.toDouble();

Thanks to @jamesdlin who actually gave this answer in a comment to my previous answer...

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You can also use:

int x = 15;
double y = x + .0;
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最佳答案

In Dart 2.1, integer literals may be directly used where double is expected. (See https://github.com/dart-lang/sdk/issues/34355.)

Note that this is syntactic sugar and applies only to literals. int variables still won't be automatically promoted to double, so code like:

double reciprocal(double d) => 1 / d;


int x = 42;
reciprocal(x);

would fail, and you'd need to do:

reciprocal(x.toDouble());
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From this attempt:

class Useless{
double field;
Useless(num input){
field = input.toDouble();
}
}

You can use the parse method of the double class which takes in a string.

class Useless{
double field;
Useless(num input){
field = double.parse(input.toString()); //modified line
}
}

A more compact way of writing the above class using constructor's initialisers is:

class Useless{
double _field;
Useless(double field):_field=double.parse(field.toString());
}
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I'm using a combination:

static double checkDouble(dynamic value) {
if (value is String) {
return double.parse(value);
} else if (value is int) {
return 0.0 + value;
} else {
return value;
}
}
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Since all divisions in flutter result to a double, the easiest thing I did to achieve this was just to divide the integer value with 1: i.e. int x = 15; double y = x /1;

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use toDouble() method.
For e.g.:

int a = 10
print(a.toDouble)
//or store value in a variable and then use
double convertedValue = a.toDouble()
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This is how you can cast from int to double int a = 2; double b = a*1.0;


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