iOS中非常强大的过滤器:NSPredicate

最新推荐文章于 2021-07-23 16:27:24 发布

oldcatwarrior

最新推荐文章于 2021-07-23 16:27:24 发布

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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

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

那传入的初始化NSString到底要满足怎样的格式呢？

(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

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

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

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

//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

//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

//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

//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];