iOS: NSString 替换 Unicode 字符

- (NSString *)stringByReplacingUnicodeWithUTF8 {
    NSString *tempStr1 = [self stringByReplacingOccurrencesOfString:@"\\u"withString:@"\\U"];
    if (![tempStr1 containsString:@"\\U"]) {
        return self;
    }
    NSString *tempStr2 = [tempStr1 stringByReplacingOccurrencesOfString:@"\""withString:@"\\\""];
    NSString *tempStr3 = [[@"\""stringByAppendingString:tempStr2]stringByAppendingString:@"\""];
    NSData *tempData = [tempStr3 dataUsingEncoding:NSUTF8StringEncoding];
    NSString *returnStr = [NSPropertyListSerialization propertyListWithData:tempData options:NSPropertyListImmutable format:NULL error:nil];
    return [returnStr stringByReplacingOccurrencesOfString:@"\\r\\n"withString:@"\n"];
}