String in Dart

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Category: Type | Language: Dart

In Dart, there are multiple ways to check if a string is a number.

Method 1: Using RegExp

Here's an example that uses a regular expression to check if a string is a number:

bool isNumber(String string) {
  final numberRegex = RegExp(r'^-?(([0-9]*)|(([0-9]*)\.([0-9]*)))



            
            
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);
  return numberRegex.hasMatch(string);
}

In this regular expression, ^ and $ represent the start and end of the string, -? matches a hyphen (minus sign) optionally, ([0-9]*) matches any number of digits, and (([0-9]*)\.([0-9]*)) matches numbers with decimal points. This method returns true if the string is a number and false otherwise.

Example usage:

print(isNumber('123')); // true

print(isNumber('-123')); // true

print(isNumber('123.45')); // true

print(isNumber('abc')); // false

Method 2: Using tryParse()

Here's an example that uses the tryParse function to check if a string is a number:

bool isNumber(String string) {
  return double.tryParse(string) != null;
}

This method returns true if the string is a number and false otherwise. double.tryParse() returns a double value if the string is a number, and returns null otherwise.

Example usage:

print(isNumber('123')); // true

print(isNumber('-123')); // true

print(isNumber('123.45')); // true

print(isNumber('abc')); // false

Both methods are valid and it depends on the situation on which one to use.

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