How to get substring of NSString?

问题:

If I want to get a value from the NSString @"value:hello World:value", what should I use?

The return value I want is @"hello World".

回答1:

Option 1:

NSString *haystack = @"value:hello World:value";
NSString *haystackPrefix = @"value:";
NSString *haystackSuffix = @":value";
NSRange needleRange = NSMakeRange(haystackPrefix.length,
                                  haystack.length - haystackPrefix.length - haystackSuffix.length);
NSString *needle = [haystack substringWithRange:needleRange];
NSLog(@"needle: %@", needle); // -> "hello World"

Option 2:

NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:@"^value:(.+?):value$" options:0 error:nil];
NSTextCheckingResult *match = [regex firstMatchInString:haystack options:NSAnchoredSearch range:NSMakeRange(0, haystack.length)];
NSRange needleRange = [match rangeAtIndex: 1];
NSString *needle = [haystack substringWithRange:needleRange];

This one might be a bit over the top for your rather trivial case though.

Option 3:

NSString *needle = [haystack componentsSeparatedByString:@":"][1];

This one creates three temporary strings and an array while splitting.

---

All snippets assume that what's searched for is actually contained in the string.

回答2:

Here's a slightly less complicated answer:

NSString *myString = @"abcdefg";
NSString *mySmallerString = [myString substringToIndex:4];

See also substringWithRange and substringFromIndex

回答3:

Here's a simple function that lets you do what you are looking for:

- (NSString *)getSubstring:(NSString *)value betweenString:(NSString *)separator
{
    NSRange firstInstance = [value rangeOfString:separator];
    NSRange secondInstance = [[value substringFromIndex:firstInstance.location + firstInstance.length] rangeOfString:separator];
    NSRange finalRange = NSMakeRange(firstInstance.location + separator.length, secondInstance.location);

    return [value substringWithRange:finalRange];
}

Usage:

NSString *myName = [self getSubstring:@"This is my :name:, woo!!" betweenString:@":"];

回答4:

Here is a little combination of @Regexident Option 1 and @Garett answers, to get a powerful string cutter between a prefix and suffix, with MORE...ANDMORE words on it.

NSString *haystack = @"MOREvalue:hello World:valueANDMORE";
NSString *prefix = @"value:";
NSString *suffix = @":value";
NSRange prefixRange = [haystack rangeOfString:prefix];
NSRange suffixRange = [[haystack substringFromIndex:prefixRange.location+prefixRange.length] rangeOfString:suffix];
NSRange needleRange = NSMakeRange(prefixRange.location+prefix.length, suffixRange.location);
NSString *needle = [haystack substringWithRange:needleRange];
NSLog(@"needle: %@", needle);

回答5:

Use this also

NSString *ChkStr = [MyString substringWithRange:NSMakeRange(5, 26)];

Note - Your NSMakeRange(start, end) should be NSMakeRange(start, end- start);