swift的替代解决方案:

要使两者都大写:

e.g:

if ("ABcd".uppercased() == "abcD".uppercased()){
}

或使两者都小写:

e.g:

if ("ABcd".lowercased() == "abcD".lowercased()){
}

来检查iPhone ContactApp中的前缀

([string rangeOfString:prefixString options:NSCaseInsensitiveSearch].location == 0)

这个博客对我很有用

NSMutableArray *arrSearchData;  
NSArray *data=[arrNearByData objectAtIndex:i];
NSString *strValue=[NSString stringWithFormat:@"%@", [data valueForKey:@"restName"]];
NSRange r = [strValue rangeOfString:key options:NSCaseInsensitiveSearch];

if(r.location != NSNotFound)
{
     [arrSearchData addObject:data];
}

在macOS上，你可以简单地使用-[NSString isCaseInsensitiveLike:]，它返回BOOL值就像- isequal:一样。

if ([@"Test" isCaseInsensitiveLike: @"test"])
    // Success

- (NSComparisonResult)caseInsensitiveCompare:(NSString *)aString

if( [@"Some String" caseInsensitiveCompare:@"some string"] == NSOrderedSame ) {
  // strings are equal except for possibly case
}

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