Preface
Today I ran into a requirement: the PM asked that the input field strip out anything that isn’t a letter, number, or Chinese character.
With this question in mind, today’s article begins.
Preparation
Create a demo with the following code:
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@interface ViewController ()
@property (weak, nonatomic) IBOutlet UITextField *input;
@property (weak, nonatomic) IBOutlet UILabel *label;
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
self.input.delegate = self;
[self.input addTarget:self action:@selector(textChange:) forControlEvents:UIControlEventEditingChanged];
}
// Called when the text content changes
- (void)textChange:(UITextField *)textField
{
// Call the relevant method here to filter the string and display it
self.label.text = //...;
}
After searching around online, most solutions use predicates to check whether something is included, but very few actually process the string.
I found 3 ways to process the string:
- Approach 1: filter with a predicate
- Approach 2: filter with a regular expression, increasing the length of the string being matched
- Approach 3: filter the string with a streamlined regular expression
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方案1
- (NSString *)filterString1:(NSString *)str {
NSString *regex = @"^[a-zA-Z0-9\u4e00-\u9fa5]+";
NSPredicate *pred = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", regex];
NSMutableString * retStr = [NSMutableString string];
for(NSInteger i=0; i< [str length];i++){
NSRange range = NSMakeRange(i, 1);
NSString *character = [str substringWithRange:range];
if([pred evaluateWithObject:character])
{
[retStr appendString:character];
}
}
return retStr;
}
This approach works, but the code is a bit verbose; still, it gets the job done.
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// Approach 2
- (NSString *)filterString2:(NSString *)str {
NSString *regex = @"[^a-zA-Z0-9\u4e00-\u9fa5]";
NSMutableString *mstr = [NSMutableString stringWithFormat:@"%@", str];
NSUInteger i = [mstr replaceOccurrencesOfString:regex withString:@"" options:NSRegularExpressionSearch range:NSMakeRange(0, mstr.length)];
return [NSString stringWithFormat:@"%@-长度:%zd",mstr,i];
}
The same approach uses the
replaceOccurrencesOfString:withString:options:range:method to replace strings with a regular expression.
Below we streamline it to two lines of code:
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// Approach 3
- (NSString *)filterString3:(NSString *)str {
NSString *regex = @"[^a-zA-Z0-9\u4e00-\u9fa5]";
return [str stringByReplacingOccurrencesOfString:regex withString:@"" options:NSRegularExpressionSearch range:NSMakeRange(0, str.length)];
}
In the end, Approach 3 gives good expected results; it’s recommended.
Summary
Some problems are encountered at work, and I hope to record and share them here to learn together.
The end.