22 May 2024 Leave a comment Tech-Help
When working with strings in Objective-C, you might need to check if a string contains another substring. This is a common requirement, and there are several ways to achieve this. Below, we will explore the most effective methods to perform this check, ensuring both compatibility and efficiency.
Using rangeOfString: Method
The rangeOfString: method is a robust way to check if a string contains another string. This method returns an NSRange struct, which indicates the location and length of the substring if it exists.
NSString *string = @"hello bla bla";
if ([string rangeOfString:@"bla"].location == NSNotFound) {
NSLog(@"string does not contain bla");
} else {
NSLog(@"string contains bla!");
}
This approach is reliable and works across different versions of iOS and macOS.
Using containsString: Method (iOS 8.0+ and macOS 10.10+)
Starting from iOS 8.0 and macOS 10.10, the NSString class includes a native containsString: method, which simplifies the process:
NSString *string = @"hello bla bla";
if ([string containsString:@"bla"]) {
NSLog(@"string contains bla!");
} else {
NSLog(@"string does not contain bla");
}
This method is more concise and easier to read. However, it is crucial to ensure that your application runs on iOS 8.0+ or macOS 10.10+ to avoid compatibility issues.
Case-Insensitive Search
If you need to perform a case-insensitive search, you can use the rangeOfString:options: method with the NSCaseInsensitiveSearch option:
NSString *string = @"hello bla bla";
NSRange range = [string rangeOfString:@"BLA" options:NSCaseInsensitiveSearch];
if (range.location == NSNotFound) {
NSLog(@"string does not contain BLA");
} else {
NSLog(@"string contains BLA!");
}
Creating a Custom Category for Older Versions
For compatibility with older versions of iOS and macOS, you can create a custom category for NSString:
@interface NSString (SubstringSearch)
- (BOOL)containsString:(NSString *)substring;
@end
@implementation NSString (SubstringSearch)
- (BOOL)containsString:(NSString *)substring {
NSRange range = [self rangeOfString:substring];
return range.location != NSNotFound;
}
@end
This approach ensures that the containsString: method is available regardless of the OS version.
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