//判断两字符串是否相等
- (BOOL)isEqualToString:(NSString *)aString;

//判断开头是否包含该字符串
- (BOOL)hasPrefix:(NSString *)aString;

//判断结尾是否包含该字符串
- (BOOL)hasSuffix:(NSString *)aString;

//该字符串在那个位置
- (NSRange)rangeOfString:(NSString *)aString;