How to convert a double to an int in Dart?

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?

Round it using the round() method:

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

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

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;

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

---

Dart round double to int

Using round() method, we can get an integer closest to a double.

For example:

int num1 = (2.3).round();
// 2

int num2 = (2.5).round();
// 3

int num3 = (-2.3).round();
// -2

int num4 = (-2.5).round();
// -3

You can also try to those methods convert double to int in a Flutter

  double x = 2.5;
 
  int a = x.toInt();
  int b = x.truncate();
  int c = x.round();
  int d = x.ceil();
  int e = x.floor();
 
  print(a); // 2
  print(b); // 2
  print(c); // 3
  print(d); // 3
  print(e); // 2

Its easy,

(20.8).round()

For String,

double.tryParse(20.8).round()

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()

Try this!

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

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())