- (NSComparisonResult)caseInsensitiveCompare:(NSString *)aString

如果你想要更多的控制，而不仅仅是不区分大小写，另一个选择是:

[someString compare:otherString options:NSCaseInsensitiveSearch];

数字搜索和变音符不敏感是两个方便的选择。

- (NSComparisonResult)caseInsensitiveCompare:(NSString *)aString

 NSString *stringA;
 NSString *stringB;

 if (stringA && [stringA caseInsensitiveCompare:stringB] == NSOrderedSame) {
     // match
 }

注意:stringA &&是必需的，因为当stringA为nil时:

 stringA = nil;
 [stringA caseInsensitiveCompare:stringB] // return 0

所以NSOrderedSame也被定义为0。

下面的例子是一个典型的陷阱:

 NSString *rank = [[NSUserDefaults standardUserDefaults] stringForKey:@"Rank"];
 if ([rank caseInsensitiveCompare:@"MANAGER"] == NSOrderedSame) {
     // what happens if "Rank" is not found in standardUserDefaults
 }

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

文档位于搜索和比较方法

一种新的方法。iOS 8

let string: NSString = "Café"
let substring: NSString = "É"

string.localizedCaseInsensitiveContainsString(substring) // true