How to convert a double to an int in Dart?

Question

The following produces the below error:

int calc_ranks(ranks)
{
  double multiplier = .5;
  return multiplier * ranks;
}

The return type double is not a int, as defined by the method calc_ranks. How do I round/cast to an int?

Answer 1

Round it using the round() method:

int calc_ranks(ranks) {
    double multiplier = .5;
    return (multiplier * ranks).round();
}

Answer 2

You can use any of the following.

double d = 20.5;

int i = d.toInt(); // i = 20
int i = d.round(); // i = 21
int i = d.ceil();  // i = 21
int i = d.floor(); // i = 20

Answer 3

You can simply use toInt() to convert a num to an int.

int calc_ranks(ranks)
{
  double multiplier = .5;
  return (multiplier * ranks).toInt();
}

Note that to do exactly the same thing you can use the Truncating division operator :

int calc_ranks(ranks) => ranks ~/ 2;

Answer 4

I see a lot of answers, but with less description. Hope my answer will add some value. Lets initalize the variable, and see how it will change with different methods.

 double x = 8.5;

toInt()

It truncates the decimal value.

 int a = x.toInt();
 print(a); // 8

---

truncate()

It also truncates the decimal value.

 int b = x.truncate();
 print(b); // 8

---

round()

It returns the closest integer. It uses half up rounding mode.

  int c = x.round();
  print(c); // 9

---

ceil()

It returns the closest integer greater than the value.

  int c = x.ceil();
  print(c); // 9

---

floor()

It returns the closest integer smaller than the value.

  int c = x.floor();
  print(c); // 8

---

Answer 5

I looked at the answers above and added some more answers to make it a little easier to understand.

double value = 10.5;

Using toInt()

void main(){
  double value = 10.5;
  var y = value.toInt();
  print(y);
  print(y.runtimeType);
}

Using round()

The round() method returns the closest integer to the double.

void main(){
  double value = 9.6;
  var b = value.round();
  print(b);
  print(b.runtimeType);
}

Using ceil()

The ceil() method returns the smallest integer that is equal or greater than the given double.

void main(){
  double value = 9.5;
  var d = value.ceil();
  print(d);
  print(d.runtimeType);
}

Using floor()

The floor() method returns the greatest integer not greater than the given double.

void main(){
  double value = 10.9;
  var j = value.floor();
  print(j);
  print(j.runtimeType);
}

Conclusion

We’ve gone through 4 different techniques to convert a double to an integer in Dart and Flutter. You can choose from the method that fits your use case to solve your problem. Flutter is awesome and provides a lot of amazing features.

Answer 6

To convert double to int just this: division

double01 ~/ double02

PS: The operator x ~/ y is more efficient than (x / y).toInt().

Multiplication, addition and subtraction

(double01 * double02).toInt
(double01 + double02).toInt
(double01 - double02).toInt

Answer 7

Its easy,

(20.8).round()

For String,

double.tryParse(20.8).round()

Answer 8

from string to int ->

1. if you string in int format like '10' then use ---->

   int.parse(value)

   but if string in double format like '10.6' then use like this ---->

   double.parse(value).toInt()

2. convert double to int

   doubleValue.toInt()

Answer 9

Try this!

int calc_ranks(ranks)
{
  double multiplier = .5;
  return (multiplier * ranks).truncate();
}

Answer 10

    class CurrencyUtils{
    
      static int doubletoint(double doublee) {
        double multiplier = .5;
        return (multiplier * doublee).round();
      }
    }
    
    ----------------------
    
    
    CustomText( CurrencyUtils.doubletoint(
double.parse(projPageListss[0].budget.toString())
).toString(),
         fontSize: 20,
         color: Colors.white,
         font: Font.QuicksandSemiBold,
                                            ), 

Answer 11

There's another alternative, you can first cast the double to 'num' datatype and then convert to int using toInt().

  double multiplier = .5;
  return ((multiplier * ranks) as num).toInt();

The num type is an inherited data type of the int and double types. You can cast both int and double to num, then cast it again to whatever you want

(double -> use toDouble(), int -> use toInt())