谓词： NSPredicate

• 1.比较操作

• 2.字符串常规操作

• 3.范围

• 4.通配符

• 5.逻辑运算符

• 6.正则表达式

• 判断是不是字母，判断是不是数字，判断是是不是字母和数字

  // If my string contains ony letters- (BOOL)containsOnlyLetters{    NSCharacterSet *letterCharacterset = [[NSCharacterSet letterCharacterSet] invertedSet];    return ([self rangeOfCharacterFromSet:letterCharacterset].location == NSNotFound);}// If my string contains only numbers- (BOOL)containsOnlyNumbers{    NSCharacterSet *numbersCharacterSet = [[NSCharacterSet characterSetWithCharactersInString:@"0123456789"] invertedSet];    return ([self rangeOfCharacterFromSet:numbersCharacterSet].location == NSNotFound);}// If my string contains letters and numbers- (BOOL)containsOnlyNumbersAndLetters{    NSCharacterSet *numAndLetterCharSet = [[NSCharacterSet alphanumericCharacterSet] invertedSet];    return ([self rangeOfCharacterFromSet:numAndLetterCharSet].location == NSNotFound);}复制代码