Predicate

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);
  }