How to check Type of a Variable in Flutter

Updated: January 18, 2023 By: A Goodman One comment

To check the type of a variable in Flutter and Dart, you can use the runtimeType property.

Example

The code:

void main(){
  var a = 'Apple';
  var b = 100;
  var c = [1, 2, 3, 4, 5];
  var d = {
    "name": "John Doe",
    "age" : 40
  };
  var e = 1.14;
  
  print(a.runtimeType);
  print(b.runtimeType);
  print(c.runtimeType);
  print(d.runtimeType); 
  print(e.runtimeType);
}

Output:

String
int
List<int>
_InternalLinkedHashMap<String, Object>
double

If you want to avoid warnings (just warnings, not errors) that come with the print() function, you can use do a check with kDebugmode like this:

import 'package:flutter/foundation.dart';

void main() {
  var a = 'Apple';
  var b = 100;
  var c = [1, 2, 3, 4, 5];
  var d = {"name": "John Doe", "age": 40};
  var e = 1.14;

  if (kDebugMode) {
    print(a.runtimeType);
    print(b.runtimeType);
    print(c.runtimeType);
    print(d.runtimeType);
    print(e.runtimeType);
  }
}

Further reading:

You can also take a tour around our Flutter topic page and Dart topic page to see the latest tutorials and examples.

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Hocine
Hocine
11 months ago

Thank you, That was helpful.

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