NSString比较在Objective-C中不起作用

NSString *string1 = @"hello";
NSString *string2 = @"world";

NSComparisonResult result = [string1 compare:string2];

if (result == NSOrderedAscending) {
    NSLog(@"string1 在字典顺序中位于 string2 之前");
} else if (result == NSOrderedDescending) {
    NSLog(@"string1 在字典顺序中位于 string2 之后");
} else {
    NSLog(@"string1 和 string2 相等");
}

NSString *string1 = @"hello";
NSString *string2 = @"Hello";

NSComparisonResult result = [string1 caseInsensitiveCompare:string2];

if (result == NSOrderedAscending) {
    NSLog(@"string1 在字典顺序中位于 string2 之前");
} else if (result == NSOrderedDescending) {
    NSLog(@"string1 在字典顺序中位于 string2 之后");
} else {
    NSLog(@"string1 和 string2 相等");
}