iOS 大写字母与小写字母之间的转换

实现中文名取到其首字母的代码

- (NSMutableString *)firstCharactor:(NSString *)aString
{
    NSMutableString *strSum = [[NSMutableString alloc]init];
    for (int i = 0 ; i < aString.length ; i++) {
        //转成了可变字符串
        NSMutableString *str = [NSMutableString stringWithString:[aString substringWithRange:NSMakeRange(i, 1)]];
        NSLog(@"---%@",str);
        //先转换为带声调的拼音
        CFStringTransform((CFMutableStringRef)str,NULL, kCFStringTransformMandarinLatin,NO);
        //再转换为不带声调的拼音
        CFStringTransform((CFMutableStringRef)str,NULL, kCFStringTransformStripDiacritics,NO);
        //转化为大写拼音
        NSString *pinYin = [str lowercaseString];
        NSLog(@"---%@",pinYin);
        //获取并返回首字母
        strSum = [[NSMutableString alloc]initWithString:[strSum stringByAppendingString:[pinYin substringToIndex:1]]];
    }
    NSLog(@"拼音%@",strSum);
    return strSum;
}

使用 lowercaseString，uppercaseString，大写字母转化为小写字母

- (void)test{
    NSString *testString = @"Hello World";

    // lower case
    NSString *lowerCaseString1 = [testString lowercaseString];
    NSString *lowerCaseString2 = testString.lowercaseString;

    // upper case
    NSString *upperCaseString1 = [lowerCaseString1 uppercaseString];
    NSString *upperCaseString2 = lowerCaseString1.uppercaseString;

    NSLog(@"lowerCaseString1: %@",lowerCaseString1);//hello world
    NSLog(@"lowerCaseString2: %@",lowerCaseString2);//hello world
    NSLog(@"upperCaseString1: %@",upperCaseString1);//HELLO WORLD
    NSLog(@"upperCaseString2: %@",upperCaseString2);//HELLO WORLD

    // capitalize the first word of the sentence
    NSString *txt = @"hi my friends!";
    txt = [txt stringByReplacingCharactersInRange:NSMakeRange(0,1) withString:[[txt substringToIndex:1] uppercaseString]];
    NSLog(@"txt: %@", txt);//Hi my friends!
}