In the realm of Dart and Flutter development, the ability to seamlessly parse strings into numerical values is essential. This tutorial navigates through the intricacies of converting strings into integers and doubles using parse() and tryParse() methods, along with handling exceptions and converting hexadecimal strings.
Table of Contents
String to int in Flutter
Parsing strings into numbers, whether integers or doubles, is a common task in programming. Dart provides methods like parse() and tryParse() to achieve this. In this tutorial, we’ll explore how to parse strings into numbers in Dart and Flutter, covering both integer and double conversions. Additionally, we’ll discuss handling exceptions for invalid input strings and converting hexadecimal strings to integers.
Parse a String into an int in Dart/Flutter
Using parse() method
To convert a string into an integer, Dart offers the int.parse() method:
var n = int.parse('42');
// 42The input string can be signed (negative or positive):
var n1 = int.parse('-42');
// -42
var n2 = int.parse('+42');
// 42Radix – Hex string to int
The int.parse() method supports converting strings into numbers with a radix in the range of 2 to 36. For example, converting a hexadecimal string into an integer:
var n_16 = int.parse('FF', radix: 16);
// 255Handling Exceptions
If the input string isn’t a valid integer, Dart throws a FormatException. To handle this, we can use a try-catch block:
try {
var n = int.parse('n42');
print(n);
} on FormatException {
print('Format error!');
}
// Format error!Using tryParse() method
Instead of using int.parse() with an onError parameter, Dart provides int.tryParse():
var n0 = int.tryParse('42');
// 42
var n1 = int.tryParse('-42');
// -42
var n2 = int.tryParse('FF', radix: 16);
// 255Parse a String into a double in Dart/Flutter
Using parse() method
Similarly, Dart’s double.parse() method converts strings into double values:
var n1 = double.parse('4.2');
// 4.2
var n2 = double.parse('0.');
// 0.0
// Other examples omitted for brevityHandling Exceptions
If the input string isn’t a valid double, Dart throws a FormatException, which can be handled with a try-catch block:
try {
var n = double.parse('n4.2');
print(n);
} on FormatException {
print('Format error!');
}
// Format error!Using tryParse() method
Dart’s double.tryParse() method returns null for invalid input strings instead of throwing an exception:
double n = double.tryParse('n4.2');
// nullBy checking for null, we can handle invalid input gracefully:
double n = double.tryParse('n4.2') ?? -1;
// -1.0How to Cast a String to an Integer in Dart
Casting a string to an integer in Dart is straightforward using the int.parse() method. This method takes a string as input and converts it into an integer value.
import 'dart:convert';
void main() {
var a = 10; // An integer
var b = "20"; // A string
var c = int.parse(b);
print(a + c);
}The int.parse() method can also handle hexadecimal strings, indicated by a preceding ‘0x’. For instance:
import 'dart:convert';
void main() {
var a = "0x1E"; // Hexadecimal value for 30
var b = int.parse(a);
print(b);
}If the input string is invalid, such as containing characters other than radix-10 or hexadecimal digits, int.parse() will throw a FormatException.
Also read:
String to int Flutter: How to Parse a String into a Number with Dart
Flutter 4.0: Transforming Cross-Platform Development
Information in Table format
| Topic | Description |
|---|---|
| How to Parse a String into a Number | Parsing strings into numbers, whether integers or doubles, is a common task in programming. Dart provides methods like parse() and tryParse() to achieve this. In this tutorial, we’ll explore how to parse strings into numbers in Dart and Flutter, covering both integer and double conversions. Additionally, we’ll discuss handling exceptions for invalid input strings and converting hexadecimal strings to integers. |
| Parse a String into an int in Dart/Flutter | – Using parse() method: Convert a string into an integer using int.parse(). The input string could be signed (+/-). – Radix – Hex string to int: Convert a hexadecimal string into an integer. – Handling Exceptions: If the input string isn’t a valid integer, Dart throws a FormatException. Using try-catch block or tryParse() method for error handling. |
| Parse a String into a double in Dart/Flutter | – Using parse() method: Convert a string into a double using double.parse(). – Handling Exceptions: If the input string isn’t a valid double, Dart throws a FormatException. Using try-catch block or tryParse() method for error handling. – Using tryParse() method: Convert a string into a double using double.tryParse(). Returns null for invalid input strings. |
| How to Cast a String to an Integer in Dart | Casting a string to an integer in Dart is straightforward using the int.parse() method. This method takes a string as input and converts it into an integer value. The int.parse() method can also handle hexadecimal strings, indicated by a preceding ‘0x’. If the input string is invalid, such as containing characters other than radix-10 or hexadecimal digits, int.parse() will throw a FormatException. |
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FAQs
How do I parse a string into a number in Dart/Flutter?
To parse a string into a number in Dart/Flutter, you can use the parse() and tryParse() methods provided by Dart. These methods allow you to convert strings into integers or doubles. The parse() method converts a string into a number and throws a FormatException if the input is invalid, while the tryParse() method returns null for invalid input strings.
What is the difference between parse() and tryParse() in Dart?
The main difference between parse() and tryParse() is how they handle invalid input strings. The parse() method throws a FormatException if the input string is not a valid number, while the tryParse() method returns null for invalid input strings, allowing you to handle errors more gracefully.
How can I handle exceptions when parsing strings into numbers in Dart?
Exceptions can be handled using a try-catch block or by providing an onError parameter to the parse() method. If the input string is not a valid number, Dart will throw a FormatException, which can be caught and handled accordingly.
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Can I convert hexadecimal strings into integers in Dart/Flutter?
Yes, Dart provides support for converting hexadecimal strings into integers using the parse() method. You can specify the radix parameter to indicate the base of the number system. For example, int.parse('FF', radix: 16) will convert the hexadecimal string ‘FF’ into the integer 255.
How do I cast a string to an integer in Dart?
To cast a string to an integer in Dart, you can use the int.parse() method. This method takes a string as input and converts it into an integer value. If the input string is not a valid number, int.parse() will throw a FormatException, which can be caught and handled accordingly. Additionally, int.parse() can handle hexadecimal strings by specifying the ‘0x’ prefix.