在APPLE的官方Demo：UICatalog中實現UISearchBar模糊搜索功能是這么做的：
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是列表的全部結果，self.visibleResults是輸入搜索詞后出現的模糊匹配結果。流程如下圖所示：
從上述代碼可以看到，APPLE獲取到模糊搜索結果所用的代碼僅僅兩行。由此可見，NSPredicate的功能不可小覷。這也是本文的目的，全方位地介紹一下在cocoa框架下的搜索匹配利器：NSPredicate。Cocoa框架中的NSPredicate用於查詢，原理和用法都類似於SQL中的where，作用相當於數據庫的過濾取。
1、初始化
NSPredicate *ca = [NSPredicate predicateWithFormat:(NSString *), ...];
那傳入的初始化NSString到底要滿足怎樣的格式呢？
(1)比較運算符>,<,==,>=,<=,!=
可用於數值及字符串
例：@"number > 100"
(2)范圍運算符：IN、BETWEEN
例：@"number BETWEEN {1,5}"
@"address IN {'shanghai','beijing'}"
(3)字符串本身:SELF
例：@“SELF == ‘APPLE’"
(4)字符串相關：BEGINSWITH、ENDSWITH、CONTAINS
例：@"name CONTAIN[cd] 'ang'" //包含某個字符串
@"name BEGINSWITH[c] 'sh'" //以某個字符串開頭
@"name ENDSWITH[d] 'ang'" //以某個字符串結束
注:[c]不區分大小寫，[d]不區分發音符號即沒有重音符號，[cd]既不區分大小寫，也不區分發音符號。
(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)正則表達式：MATCHES
例：NSString *regex = @"^A.+e$"; //以A開頭，e結尾
@"name MATCHES %@",regex
2、使用
2.1 場景1：NSArray過濾，也就是文章開頭的場景
NSArray *array = [[NSArray alloc]initWithObjects:@"beijing",@"shanghai",@"guangzou",@"wuhan", nil];
NSString *string = @"ang";
NSPredicate *pred = [NSPredicate predicateWithFormat:@"SELF CONTAINS %@",string];
NSLog(@"%@",[array filteredArrayUsingPredicate:pred]);
2.2 場景2：判斷字符串首字母是否為字母
NSString *regex = @"[A-Za-z]+";
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", regex];
if ([predicate evaluateWithObject:aString]) {
}
2.3 場景3：字符串替換
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 場景4：截取字符串
//組裝一個字符串，需要把里面的網址解析出來
NSString *urlString=@"<meta/><link/><title>1Q84 BOOK1</title></head><body>";
//NSRegularExpression類里面調用表達的方法需要傳遞一個NSError的參數。下面定義一個
NSError *error;
//http+:[^\\s]* 這個表達式是檢測一個網址的。(?<=title\>).*(?=</title)截取html文章中的<title></title>中內文字的正則表達式
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];
//從urlString當中截取數據
NSString *result=[urlString substringWithRange:resultRange];
//輸出結果
NSLog(@"->%@<-",result);
}
}
2.5 場景5：判斷是否是手機號碼或者電話號碼
//組裝一個字符串，需要把里面的網址解析出來
NSString *urlString=@"<meta/><link/><title>1Q84 BOOK1</title></head><body>";
//NSRegularExpression類里面調用表達的方法需要傳遞一個NSError的參數。下面定義一個
NSError *error;
//http+:[^\\s]* 這個表達式是檢測一個網址的。(?<=title\>).*(?=</title)截取html文章中的<title></title>中內文字的正則表達式
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];
//從urlString當中截取數據
NSString *result=[urlString substringWithRange:resultRange];
//輸出結果
NSLog(@"->%@<-",result);
}
}
2.6 場景6：驗證郵箱、電話號碼有效性
//是否是有效的正則表達式
+(BOOL)isValidateRegularExpression:(NSString *)strDestination byExpression:(NSString *)strExpression
{
NSPredicate *predicate = [NSPredicatepredicateWithFormat:@"SELF MATCHES %@", strExpression];
return [predicate evaluateWithObject:strDestination];
}
//驗證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;
}
//驗證電話號碼
+(BOOL)isValidateTelNumber:(NSString *)number {
NSString *strRegex = @"[0-9]{1,20}";
BOOL rt = [CommonTools isValidateRegularExpression:number byExpression:strRegex];
return rt;
}
2.7 場景7：NSDate篩選
//日期在十天之內: NSDate *endDate = [[NSDate date] retain]; NSTimeInterval timeInterval= [endDate timeIntervalSinceReferenceDate]; timeInterval -=3600*24*10; NSDate *beginDate = [[NSDate dateWithTimeIntervalSinceReferenceDate:timeInterval] retain]; //對coredata進行篩選(假設有fetchRequest) NSPredicate *predicate_date = [NSPredicate predicateWithFormat:@"date >= %@ AND date <= %@", beginDate,endDate]; [fetchRequest setPredicate:predicate_date]; //釋放retained的對象 [endDate release]; [beginDate release];