Dart/Flutter How to Check string contains alphabetic number
Dart String characters Examples
The string
is a group of characters enclosed in single or double-quotes.
Characters can be any of the following types
alphabetic characters
: Each character contains a letter from lowercase - a to z and uppercase - A to Z.- `alphanumeric characters: contain alphabetic and numeric characters.
Special characters
: a character is like %,# ..etc excluding alphabetic and numeric characters.numbers
:
a character is like numbers are called numeric characters.
In this post, You will learn the following things in Dart.
-
Check String contains alphabetic
-
Check String contains numbers
-
Check String contains alphabetic using a regular expression
-
Check String contains alphanumeric and special characters
How to check if a string contains numbers?
This example checks if a string contains numeric digits in it.
The string has a contains
method that checks a given string with the matched pattern.
bool contains(Pattern other, [int startIndex = 0])
The pattern is a regular expression created using the RegExp class startIndex is a starting position of a string to search for a pattern.
Here is a dart program to check
void main() {
var str = "Hello";
var str1 = "Hello123";
print(str.contains(new RegExp(r'[0-9]'))); // false
print(str1.contains(new RegExp(r'[0-9]'))); // true
}
How to check if a string contains number only
This program checks if a given string contains only numbers and no alphabets
void main() {
var str = "123";
var str1 = "Hello123";
print(str.contains(new RegExp(r'^[0-9]+$'))); // true
print(str1.contains(new RegExp(r'^[0-9]+$'))); // false
}
Example 2: How to check if a string contains alphabetic characters using Regular Expression?
Regular expressions are supported and available in dart using the RegExp
standard inbuilt package.
It includes checking regular expressions and pattern matching against a text.
The first regular expression pattern is created using the new RegExp()
RegExp
is used to check matched string, Regular Expression is used as regexp.
^[a-zA-Z]+
^
- Beginning of a string
\[
- Character group starting
a-z
- lower case letter
A-Z
- upper case letter
\]
- Character group end
\+
- one or more characters
Here is a Program to check String contains Alphabetic using a regular expression
void main() {
var str = "abc";
var str1 = "Hello123";
print(str.contains(new RegExp('^[a-zA-Z]+'))); // true
print(str1.contains(new RegExp('^[a-zA-Z]+'))); // false
}
Output:
true
false
Example 3- Check String contains Alphanumeric characters or special characters
Regular expression pattern is ^[a-zA-Z0-9_]*$ used.
It returns true
for alphabetic, numeric, and underscore characters.
return false - for special characters.
Here is a program to check a string for Alphabetic and special characters
void main() {
var str = "abc_";
var str1 = "Hello_123";
print(str.contains(new RegExp('^[a-zA-Z0-9_]*'))); // true
print(str1.contains(new RegExp('^[a-zA-Z0-9_]*'))); // true
}
When you compile and execute, the output is
true
true
Conclusion
To summarize, You learned multiple programs to check strings containing Alphabetic, numeric and special characters in the Dart language.