【原/转】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：
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
*), ...];
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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
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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:@
"SELF CONTAINS %@"
,string];
NSLog
(@
"%@"
,[array filteredArrayUsingPredicate:pred]);
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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]) {
}
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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);
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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);
}
}
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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);
}
}
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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;
}
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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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本文转自编程小翁博客园博客，原文链接：http://www.cnblogs.com/wengzilin/p/4276612.html，如需转载请自行联系原作者
