Dart: string replace related methods

Today we have such a problem , There will be several special characters in the text display ,"️", This is because I inserted it while editing , It is easy to distinguish whether it is a picture , But in the process of text display, there are , So is there a way for him not to show , The answer is yes , Next, let's take a look at

About String Some operations on this aspect in .

replaceAll

String replaceAll(pattern from,String replace)

replaceAll The first parameter is the matcher , It can be a string or a regular expression , The second parameter is the string to replace , The return value is a new string .

, I'm here to write a Demo, As you all know

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void main() {
​
 var a = ' Big front end ️ The journey ️';
 var b = ' Big front end ️';
 print(a.replaceAll('️', '')); 
 print(b.replaceAll(RegExp(r'(️)'), '')); 
​
​
​
}
​

The operation effect is as follows ：

Have you learned the above

Let's go on

replaceAllMapped

String replaceAllMapped(
​
Pattern from,
​
String replace(Match match)
​
)

replaceAllMapped The first parameter is the matcher , It can be a string or a regular , The second argument is a function , The string fragment captured by the parameter of the function , In fact, it is a mapping of the captured string fragments , Look at the function name mapped You can see .

​
void main() {
​
 var a = ' Big front end ️ The journey ️';
 var b = ' Big front end ️';
​
 print(a.replaceAllMapped('️', (Match m) => ''));
 print(b.replaceAllMapped(RegExp(r'️'), (Match m) => ''));
 
​
​
​
}
​

replaceFirst

String replaceFirst(
​
Pattern from,
​
String to,
​
[int startIndex = 0]
​
)

replaceFirst The first parameter is the match character , It can be a string or a regular , The second parameter is the string to replace , The third parameter is optional , The default is 0,. If this method matches multiple string fragments , Then it will only replace the subscript startIndex The capture of , If the subscript is larger than the length of the captured fragment , Then there will be an error

​
void main() {
​
   var d = ' Big front end tour ';
 print(d.replaceFirst(RegExp(r'\ Big '), 'jianguo', 0)); //1ccc3
}
​

4.replaceFirstMapped

String replaceFirstMapped(
​
Pattern from,
​
String replace(Match match),
​
[int startIndex = 0]
​
)

replaceFirstMapped and replaceAllMapped similar , Replace the captured string fragment startIdnex The corresponding segment , And through the function passed by the second parameter .

 var e = 'asd';
 print(e.replaceFirstMapped(RegExp(r'\w'), (Match m) => '${m[0]}${m[0]}', 2),);//asdd

5.replaceRange

String replaceRange(
​
int start,
​
int end,
​
String replacement
​
)

replaceRange The first parameter is the starting subscript , The second parameter is the ending subscript , The third parameter is the string to replace . The replaced string contains the starting subscript , Does not include end subscript , And start subscribing numbers to >=0, Less than or equal to the end subscript , The value of the end subscript must be less than or equal to the length of the string , Otherwise, an error will be reported .

​
​
 var f = '123456789';
 print(f.replaceRange(1, 3, 'replace')); //1replace456789

The above is what I use replace Some related operations ,

In the project, I also used this line of code to solve the problem .

The same is true of practical work , And a process of solving problems , As long as we insist on , There will be gains .