iOS中非常强大的过滤器:NSPredicate

来源：互联网发布：java 方法调用栈编辑：程序博客网时间：2024/05/05 22:50

在APPLE的官方Demo：UICatalog中实现UISearchBar模糊搜索功能是这么做的：

1 - (void)viewDidLoad {2     [super viewDidLoad];3 4     self.allResults = @[@"Here's", @"to", @"the", @"crazy", @"ones.", @"The", @"misfits.", @"The", @"rebels.", @"The", @"troublemakers.", @"The", @"round", @"pegs", @"in", @"the", @"square", @"holes.", @"The", @"ones", @"who", @"see", @"things", @"differently.", @"They're", @"not", @"fond", @"of", @"rules.", @"And", @"they", @"have", @"no", @"respect", @"for", @"the", @"status", @"quo.", @"You", @"can", @"quote", @"them,", @"disagree", @"with", @"them,", @"glorify", @"or", @"vilify", @"them.", @"About", @"the", @"only", @"thing", @"you", @"can't", @"do", @"is", @"ignore", @"them.", @"Because", @"they", @"change", @"things.", @"They", @"push", @"the", @"human", @"race", @"forward.", @"And", @"while", @"some", @"may", @"see", @"them", @"as", @"the", @"crazy", @"ones,", @"we", @"see", @"genius.", @"Because", @"the", @"people", @"who", @"are", @"crazy", @"enough", @"to", @"think", @"they", @"can", @"change", @"the", @"world,", @"are", @"the", @"ones", @"who", @"do."];5     6     self.visibleResults = self.allResults;7 }

 1 - (void)setFilterString:(NSString *)filterString { 2     _filterString = filterString; 3      4     if (!filterString || filterString.length <= 0) { 5         self.visibleResults = self.allResults; 6     } 7     else { 8         NSPredicate *filterPredicate = [NSPredicate predicateWithFormat:@"self contains[c] %@", filterString]; 9         self.visibleResults = [self.allResults filteredArrayUsingPredicate:filterPredicate];10     }11     12     [self.tableView reloadData];13 }

其中，self.allResults是列表的全部结果，self.visibleResults是输入搜索词后出现的模糊匹配结果。流程如下图所示：

从上述代码可以看到，APPLE获取到模糊搜索结果所用的代码仅仅两行。由此可见，NSPredicate的功能不可小觑。这也是本文的目的，全方位地介绍一下在cocoa框架下的搜索匹配利器：NSPredicate。Cocoa框架中的NSPredicate用于查询，原理和用法都类似于SQL中的where，作用相当于数据库的过滤取。

1、初始化

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NSPredicate *ca = [NSPredicate predicateWithFormat:(NSString *), ...];

那传入的初始化NSString到底要满足怎样的格式呢？

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(1)比较运算符>,<,==,>=,<=,!=
可用于数值及字符串
例：@"number > 100"
 
(2)范围运算符：IN、BETWEEN
例：@"number BETWEEN {1,5}"
      @"address IN {'shanghai','beijing'}"
 
(3)字符串本身:SELF
例：@“SELF == ‘APPLE’"
 
(4)字符串相关：BEGINSWITH、ENDSWITH、CONTAINS
例：@"name CONTAIN[cd] 'ang'"   //包含某个字符串
       @"name BEGINSWITH[c] 'sh'"     //以某个字符串开头
       @"name ENDSWITH[d] 'ang'"      //以某个字符串结束
        注:[c]不区分大小写，[d]不区分发音符号即没有重音符号，[cd]既不区分大小写，也不区分发音符号。
 
(5)通配符：LIKE
例：@"name LIKE[cd] '*er*'"    //*代表通配符,Like也接受[cd].
       @"name LIKE[cd] '???er*'"
 
(6)正则表达式：MATCHES
例：NSString *regex = @"^A.+e$";   //以A开头，e结尾
      @"name MATCHES %@",regex

2、使用

2.1 场景1：NSArray过滤，也就是文章开头的场景

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NSArray *array = [[NSArray alloc]initWithObjects:@"beijing",@"shanghai",@"guangzou",@"wuhan", nil]; 
NSString *string = @"ang"; 
NSPredicate *pred = [NSPredicate predicateWithFormat:<span style="color: #ff0000;">@"SELF CONTAINS %@",string</span>]; 
NSLog(@"%@",[array filteredArrayUsingPredicate:pred]); 

2.2 场景2：判断字符串首字母是否为字母

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NSString *regex = @"[A-Za-z]+"; 
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", regex]; 
   
if ([predicate evaluateWithObject:aString]) { 
} 

2.3 场景3：字符串替换

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NSError* error = NULL; 
NSRegularExpression* regex = [NSRegularExpression regularExpressionWithPattern:@"(encoding=\")[^\"]+(\")" 
                                                                            options:0 
                                                                            error:&error]; 
NSString* sample = @"<xml encoding=\"abc\"></xml><xml encoding=\"def\"></xml><xml encoding=\"ttt\"></xml>"; 
NSLog(@"Start:%@",sample); 
NSString* result = [regex stringByReplacingMatchesInString:sample 
                                                      options:0 
                                                       range:NSMakeRange(0, sample.length) 
                                                      withTemplate:@"$1utf-8$2"]; 
NSLog(@"Result:%@", result); 

2.4 场景4：截取字符串

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//组装一个字符串，需要把里面的网址解析出来 
NSString *urlString=@"<meta/><link/><title>1Q84 BOOK1</title></head><body>"; 
   
//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。(?<=title\>).*(?=</title)截取html文章中的<title></title>中内文字的正则表达式 
NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:@"(?<=title\\>).*(?=</title)" options:0 error:&error]; 
   
if (regex != nil) { 
    NSTextCheckingResult *firstMatch=[regex firstMatchInString:urlString options:0 range:NSMakeRange(0, [urlString length])]; 
       
    if (firstMatch) { 
        NSRange resultRange = [firstMatch rangeAtIndex:0]; 
           
        //从urlString当中截取数据 
        NSString *result=[urlString substringWithRange:resultRange]; 
        //输出结果 
        NSLog(@"->%@<-",result); 
    } 
       
} 

2.5 场景5：判断是否是手机号码或者电话号码

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//组装一个字符串，需要把里面的网址解析出来 
NSString *urlString=@"<meta/><link/><title>1Q84 BOOK1</title></head><body>"; 
   
//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。(?<=title\>).*(?=</title)截取html文章中的<title></title>中内文字的正则表达式 
NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:@"(?<=title\\>).*(?=</title)" options:0 error:&error]; 
   
if (regex != nil) { 
    NSTextCheckingResult *firstMatch=[regex firstMatchInString:urlString options:0 range:NSMakeRange(0, [urlString length])]; 
       
    if (firstMatch) { 
        NSRange resultRange = [firstMatch rangeAtIndex:0]; 
           
        //从urlString当中截取数据 
        NSString *result=[urlString substringWithRange:resultRange]; 
        //输出结果 
        NSLog(@"->%@<-",result); 
    } 
       
} 

2.6 场景6：验证邮箱、电话号码有效性

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//是否是有效的正则表达式
 
+(BOOL)isValidateRegularExpression:(NSString *)strDestination byExpression:(NSString *)strExpression
 
{
 
   NSPredicate *predicate = [NSPredicatepredicateWithFormat:@"SELF MATCHES %@", strExpression]; 
 
   return [predicate evaluateWithObject:strDestination];
 
}
 
//验证email
+(BOOL)isValidateEmail:(NSString *)email {
 
   NSString *strRegex = @"[A-Z0-9a-z._%+-]+@[A-Za-z0-9.-]+\\.[A-Za-z]{1,5}";
 
   BOOL rt = [CommonTools isValidateRegularExpression:email byExpression:strRegex];
 
   return rt;
 
}
 
//验证电话号码
+(BOOL)isValidateTelNumber:(NSString *)number {
 
   NSString *strRegex = @"[0-9]{1,20}";
 
   BOOL rt = [CommonTools isValidateRegularExpression:number byExpression:strRegex];
 
   return rt;
 
}

2.7 场景7：NSDate筛选

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//日期在十天之内:
NSDate *endDate = [[NSDate date] retain];
NSTimeInterval timeInterval= [endDate timeIntervalSinceReferenceDate];
timeInterval -=3600*24*10;
NSDate *beginDate = [[NSDate dateWithTimeIntervalSinceReferenceDate:timeInterval] retain];
//对coredata进行筛选(假设有fetchRequest)
NSPredicate *predicate_date =
[NSPredicate predicateWithFormat:@"date >= %@ AND date <= %@", beginDate,endDate];
     
[fetchRequest setPredicate:predicate_date];
//释放retained的对象
[endDate release];
[beginDate release];

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