iOS中非常强大的过滤器:NSPredicate

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：

iOS中非常强大的过滤器:NSPredicate

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

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

那传入的初始化NSString到底要满足怎样的格式呢？

123456789101112131415161718192021222324 (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

1234 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

12345 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

1234567891011 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

12345678910111213141516171819202122 //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

2.6 场景6：验证邮箱、电话号码有效性

123456789101112131415161718192021222324252627282930313233 //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

12345678910111213 //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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iOS中非常强大的过滤器:NSPredicate

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