iphone 4.0以后就开始支持正则表达式的使用了，在ios4.0中正则表达式的使用是使用NSRegularExpression类来调用。

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1. 下面一个简单的使用正则表达式的一个例子：NSRegularExpression 类

-(void)parseString{

//组装一个字符串，需要把里面的网址解析出来

NSString *urlString=@"sfdsfhttp://www.baidu.com";

//NSRegularExpression类里面调用表达的方法需要传递一个NSError的参数。下面定义一个

 NSError *error;

//http+:[^\\s]* 这个表达式是检测一个网址的。

  NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:@"http+:[^\\s]*" options:0 error:&error];

   if (regex != nil) {

   NSTextCheckingResult *firstMatch=[regex firstMatchInString:urlString options:0range:NSMakeRange(0, [urlString length])];

   if (firstMatch) {

    NSRange resultRange = [firstMatch rangeAtIndex:0]; //等同于 firstMatch.range --- 相匹配的范围

    //从urlString当中截取数据

   NSString *result=[urlString substringWithRange:resultRange];

   //输出结果

   NSLog(@"%@",result);

  }

  }

}

2.使用正则表达式来判断

//初始化一个NSRegularExpression 对象，并设置检测对象范围为：0-9

NSRegularExpression *regex2 = [NSRegularExpression regularExpressionWithPattern:@"^[0-9]*$" options:0 error:nil];

    if (regex2)

    {//对象进行匹配

       NSTextCheckingResult *result2 = [regex2 firstMatchInString:textField.text options:0 range:NSMakeRange(0, [textField.text length])];

      if (result2) {

      }

}

1。 判断邮箱格式是否正确的代码：NSPredicatel类

//利用正则表达式验证

NSPredicatel类:主要用来指定过滤器的条件,该对象可以准确的描述所需条件，对每个对象通过谓词进行筛选，判断是否与条件相匹配。谓词是指在计算机中表示计算真假值的函数。原理和用法都类似于SQL查询中的where，作用相当于数据库的过滤取。主要用于从集合中分拣出符合条件的对象，也可以用于字符串的正则匹配

-(BOOL)isValidateEmail:(NSString *)email

{

  NSString *emailRegex = @"[A-Z0-9a-z._%+-]+@[A-Za-z0-9.-]+\\.[A-Za-z]{2,4}";

  NSPredicate *emailTest = [NSPredicate predicateWithFormat:@"SELF MATCHES%@",emailRegex];

  return [emailTest evaluateWithObject:email];

}

2 。 匹配9-15个由字母/数字组成的字符串的正则表达式：

   NSString * regex = @"^[A-Za-z0-9]{9,15}$";
   NSPredicate *pred = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", regex];
   BOOL isMatch = [pred evaluateWithObject:txtfldPhoneNumber.text];

Cocoa用NSPredicate描述查询的方式，原理类似于在数据库中进行查询

用BETWEEN，IN，BEGINWITH，ENDWITH，CONTAINS，LIKE这些谓词来构造NSPredicate，必要的时候使用SELF直接对自己进行匹配

[cpp]
//基本的查询  
NSPredicate *predicate; 
predicate = [NSPredicate predicateWithFormat: @"name == 'Herbie'"]; 
   BOOL match = [predicate evaluateWithObject: car]; 
   NSLog (@"%s", (match) ? "YES" : "NO"); 
//在整个cars里面循环比较  
   predicate = [NSPredicate predicateWithFormat: @"engine.horsepower > 150"]; 
   NSArray *cars = [garage cars]; 
   for (Car *car in [garage cars]) { 
       if ([predicate evaluateWithObject: car]) { 
           NSLog (@"%@", car.name); 
       } 
   } 
//输出完整的信息  
   predicate = [NSPredicate predicateWithFormat: @"engine.horsepower > 150"]; 
   NSArray *results; 
   results = [cars filteredArrayUsingPredicate: predicate]; 
   NSLog (@"%@", results); 
//含有变量的谓词  
   NSPredicate *predicateTemplate = [NSPredicate predicateWithFormat:@"name == $NAME"]; 
   NSDictionary *varDict; 
   varDict = [NSDictionary dictionaryWithObjectsAndKeys: 
              @"Herbie", @"NAME", nil]; 
   predicate = [predicateTemplate predicateWithSubstitutionVariables: varDict]; 
   NSLog(@"SNORGLE: %@", predicate); 
   match = [predicate evaluateWithObject: car]; 
 NSLog (@"%s", (match) ? "YES" : "NO"); 
//注意不能使用$VARIABLE作为路径名，因为它值代表值  
//谓词字符窜还支持c语言中一些常用的运算符  
    
   predicate = [NSPredicate predicateWithFormat: 
                @"(engine.horsepower > 50) AND (engine.horsepower < 200)"]; 
   results = [cars filteredArrayUsingPredicate: predicate]; 
   NSLog (@"oop %@", results); 
    
   predicate = [NSPredicate predicateWithFormat: @"name < 'Newton'"]; 
   results = [cars filteredArrayUsingPredicate: predicate]; 
   NSLog (@"%@", [results valueForKey: @"name"]); 
//强大的数组运算符  
   predicate = [NSPredicate predicateWithFormat: 
                @"engine.horsepower BETWEEN { 50, 200 }"]; 
   results = [cars filteredArrayUsingPredicate: predicate]; 
   NSLog (@"%@", results); 
    
   NSArray *betweens = [NSArray arrayWithObjects: 
                        [NSNumber numberWithInt: 50], [NSNumber numberWithInt: 200], nil]; 
   predicate = [NSPredicate predicateWithFormat: @"engine.horsepower BETWEEN %@", betweens]; 
   results = [cars filteredArrayUsingPredicate: predicate]; 
   NSLog (@"%@", results); 
   predicateTemplate = [NSPredicate predicateWithFormat: @"engine.horsepower BETWEEN $POWERS"]; 
   varDict = [NSDictionary dictionaryWithObjectsAndKeys: betweens, @"POWERS", nil]; 
   predicate = [predicateTemplate predicateWithSubstitutionVariables: varDict]; 
   results = [cars filteredArrayUsingPredicate: predicate]; 
   NSLog (@"%@", results); 
//IN运算符  
   predicate = [NSPredicate predicateWithFormat: @"name IN { 'Herbie', 'Snugs', 'Badger', 'Flap' }"]; 
   results = [cars filteredArrayUsingPredicate: predicate]; 
   NSLog (@"%@", [results valueForKey: @"name"]); 
   predicate = [NSPredicate predicateWithFormat: @"SELF.name IN { 'Herbie', 'Snugs', 'Badger', 'Flap' }"]; 
   results = [cars filteredArrayUsingPredicate: predicate]; 
   NSLog (@"%@", [results valueForKey: @"name"]); 
    
   names = [cars valueForKey: @"name"]; 
   predicate = [NSPredicate predicateWithFormat: @"SELF IN { 'Herbie', 'Snugs', 'Badger', 'Flap' }"]; 
   results = [names filteredArrayUsingPredicate: predicate];//这里限制了SELF的范围  
   NSLog (@"%@", results); 
//BEGINSWITH,ENDSWITH,CONTAINS  
//附加符号，[c],[d],[cd],c表示不区分大小写，d表示不区分发音字符，cd表示什么都不区分  
   predicate = [NSPredicate predicateWithFormat: @"name BEGINSWITH 'Bad'"]; 
   results = [cars filteredArrayUsingPredicate: predicate]; 
   NSLog (@"%@", results); 
    
   predicate = [NSPredicate predicateWithFormat: @"name BEGINSWITH 'HERB'"]; 
   results = [cars filteredArrayUsingPredicate: predicate]; 
   NSLog (@"%@", results); 
    
   predicate = [NSPredicate predicateWithFormat: @"name BEGINSWITH[cd] 'HERB'"]; 
   results = [cars filteredArrayUsingPredicate: predicate]; 
   NSLog (@"%@", results); 
//LIKE运算符（通配符）  
   predicate = [NSPredicate predicateWithFormat: @"name LIKE[cd] '*er*'"]; 
   results = [cars filteredArrayUsingPredicate: predicate]; 
   NSLog (@"%@", results); 
    
   predicate = [NSPredicate predicateWithFormat: @"name LIKE[cd] '???er*'"]; 
   results = [cars filteredArrayUsingPredicate: predicate]; 
   NSLog (@"%@", results);

//基本的查询
NSPredicate *predicate;
predicate = [NSPredicate predicateWithFormat: @"name == 'Herbie'"];
   BOOL match = [predicate evaluateWithObject: car];
   NSLog (@"%s", (match) ? "YES" : "NO");
//在整个cars里面循环比较
   predicate = [NSPredicate predicateWithFormat: @"engine.horsepower > 150"];
   NSArray *cars = [garage cars];
   for (Car *car in [garage cars]) {
       if ([predicate evaluateWithObject: car]) {
           NSLog (@"%@", car.name);
       }
   }
//输出完整的信息
   predicate = [NSPredicate predicateWithFormat: @"engine.horsepower > 150"];
   NSArray *results;
   results = [cars filteredArrayUsingPredicate: predicate];
   NSLog (@"%@", results);
//含有变量的谓词
   NSPredicate *predicateTemplate = [NSPredicate predicateWithFormat:@"name == $NAME"];
   NSDictionary *varDict;
   varDict = [NSDictionary dictionaryWithObjectsAndKeys:
              @"Herbie", @"NAME", nil];
   predicate = [predicateTemplate predicateWithSubstitutionVariables: varDict];
   NSLog(@"SNORGLE: %@", predicate);
   match = [predicate evaluateWithObject: car];
 NSLog (@"%s", (match) ? "YES" : "NO");
//注意不能使用$VARIABLE作为路径名，因为它值代表值
//谓词字符窜还支持c语言中一些常用的运算符
  
   predicate = [NSPredicate predicateWithFormat:
                @"(engine.horsepower > 50) AND (engine.horsepower < 200)"];
   results = [cars filteredArrayUsingPredicate: predicate];
   NSLog (@"oop %@", results);
  
   predicate = [NSPredicate predicateWithFormat: @"name < 'Newton'"];
   results = [cars filteredArrayUsingPredicate: predicate];
   NSLog (@"%@", [results valueForKey: @"name"]);
//强大的数组运算符
   predicate = [NSPredicate predicateWithFormat:
                @"engine.horsepower BETWEEN { 50, 200 }"];
   results = [cars filteredArrayUsingPredicate: predicate];
   NSLog (@"%@", results);
  
   NSArray *betweens = [NSArray arrayWithObjects:
                        [NSNumber numberWithInt: 50], [NSNumber numberWithInt: 200], nil];
   predicate = [NSPredicate predicateWithFormat: @"engine.horsepower BETWEEN %@", betweens];
   results = [cars filteredArrayUsingPredicate: predicate];
   NSLog (@"%@", results);
   predicateTemplate = [NSPredicate predicateWithFormat: @"engine.horsepower BETWEEN $POWERS"];
   varDict = [NSDictionary dictionaryWithObjectsAndKeys: betweens, @"POWERS", nil];
   predicate = [predicateTemplate predicateWithSubstitutionVariables: varDict];
   results = [cars filteredArrayUsingPredicate: predicate];
   NSLog (@"%@", results);
//IN运算符
   predicate = [NSPredicate predicateWithFormat: @"name IN { 'Herbie', 'Snugs', 'Badger', 'Flap' }"];
   results = [cars filteredArrayUsingPredicate: predicate];
   NSLog (@"%@", [results valueForKey: @"name"]);
   predicate = [NSPredicate predicateWithFormat: @"SELF.name IN { 'Herbie', 'Snugs', 'Badger', 'Flap' }"];
   results = [cars filteredArrayUsingPredicate: predicate];
   NSLog (@"%@", [results valueForKey: @"name"]);
  
   names = [cars valueForKey: @"name"];
   predicate = [NSPredicate predicateWithFormat: @"SELF IN { 'Herbie', 'Snugs', 'Badger', 'Flap' }"];
   results = [names filteredArrayUsingPredicate: predicate];//这里限制了SELF的范围
   NSLog (@"%@", results);
//BEGINSWITH,ENDSWITH,CONTAINS
//附加符号，[c],[d],[cd],c表示不区分大小写，d表示不区分发音字符，cd表示什么都不区分
   predicate = [NSPredicate predicateWithFormat: @"name BEGINSWITH 'Bad'"];
   results = [cars filteredArrayUsingPredicate: predicate];
   NSLog (@"%@", results);
  
   predicate = [NSPredicate predicateWithFormat: @"name BEGINSWITH 'HERB'"];
   results = [cars filteredArrayUsingPredicate: predicate];
   NSLog (@"%@", results);
  
   predicate = [NSPredicate predicateWithFormat: @"name BEGINSWITH[cd] 'HERB'"];
   results = [cars filteredArrayUsingPredicate: predicate];
   NSLog (@"%@", results);
//LIKE运算符（通配符）
   predicate = [NSPredicate predicateWithFormat: @"name LIKE[cd] '*er*'"];
   results = [cars filteredArrayUsingPredicate: predicate];
   NSLog (@"%@", results);
  
   predicate = [NSPredicate predicateWithFormat: @"name LIKE[cd] '???er*'"];
   results = [cars filteredArrayUsingPredicate: predicate];
   NSLog (@"%@", results);

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