Flutter Converting String to Boolean

On top of my head, you can create an extension method for string data-type for your own need with all sorts of requirements checks and custom exceptions to beautify your desired functionalities. Here is an example:

import 'package:test/expect.dart';

void main(List<String> args) {
  String isValid = "true";

  print(isValid.toBoolean());
}

extension on String {
  bool toBoolean() {
    print(this);
    return (this.toLowerCase() == "true" || this.toLowerCase() == "1")
        ? true
        : (this.toLowerCase() == "false" || this.toLowerCase() == "0"
            ? false
            : throwsUnsupportedError);
  }
}

Here, in this example, I've created a variable named isValid in the main() method, which contains a string value. But, look closely at how I've parsed the string value to a bool value using the power with extension declared just a few lines below.

Same way, you can access the newly created string-extension method toBoolean() from anywhere. Keep in mind, if you're not in the same file where the toBoolean() extension is created, don't forget to import the proper reference.

Bonus tips: You can also access toBoolean() like this,

bool alternateValidation = "true".toBoolean();

Happy coding 😊

This example can work for you, either if is false or true:

  String isValid = "true";
  
  bool newBoolValue = isValid.toLowerCase() != "false";
  
  print(newBoolValue);

You can use extensions like this

bool toBoolean() {
   String str = this!;
   return str != '0' && str != 'false' && str != '';
}

First of All You should make the string to lowercase to prevent check the string twice then you can check if the string equal "true" or not and save the result to bool variable as below:

String isValidString = "false";  // the boolean inside string  
bool isValid = isValidString.toLowerCase() == 'true'; // check if true after lowercase
print("isValid=$isValid"); // print the result

I opened a PR for this question, I believe that in the future it will be possible to do something native.

void main() {
  
  print(bool.parse("true")); // true
  print(bool.parse("false")); //false
  print(bool.parse("TRUE")); // FormatException
  print(bool.parse("FALSE")); //FormatException
  print(bool.parse("True", caseSensitive: false)); // true
  print(bool.parse("False", caseSensitive: false)); // false
  
  if(bool.parse("true")){
    //code..
  }

}

Reference

You can simply write

isValid.parseBool()

To convert String into bool.