iOS Predicate 即謂詞邏輯。和數(shù)據(jù)庫(kù)的SQL語(yǔ)句具有相似性，都是從數(shù)據(jù)堆中根據(jù)條件進(jìn)行篩選。

使用場(chǎng)景：

1. NSPredicate給我留下最深印象的是兩個(gè)數(shù)組求交集的一個(gè)需求，如果按照一般寫法，需要2個(gè)遍歷，但NSArray提供了一個(gè)filterUsingPredicate的方法，用了NSPredicate，就可以不用遍歷！
2. 在存儲(chǔ)自定義對(duì)象的數(shù)組中，可以根據(jù)條件查詢數(shù)組中滿足條件的對(duì)象。

首先熟悉Predicate:

NSArray *array1 = [NSArray arrayWithObjects:@1,@2,@3,@5,@5,@6,@7, nil];
NSArray *array2 = [NSArray arrayWithObjects:@4,@5, nil];
***// 表示篩選array1在array2中的元素!YES！其中SELF指向filteredArrayUsingPredicate的調(diào)用者。***
/*測(cè)試方案：
NSPredicate *predicate1 = [NSPredicate predicateWithFormat:@"SELF  in %@",array2];
NSArray *temp1 = [array1 filteredArrayUsingPredicate:predicate1];
//表示array1在array2中元素
結(jié)果：
2015-11-08 10:55:19.879 NSPredicateDemo[11595:166012] obj ==5
2015-11-08 10:55:19.879 NSPredicateDemo[11595:166012] obj ==5

NSPredicate *predicate2 = [NSPredicate predicateWithFormat:@"SELF  in %@",array1];
NSArray *temp1 = [array2 filteredArrayUsingPredicate:predicate1];
結(jié)果：
2015-11-08 10:55:19.879 NSPredicateDemo[11595:166012] obj ==5
*/
NSPredicate *predicate1 = [NSPredicate predicateWithFormat:@"SELF  in %@",array2];
NSArray *temp1 = [array1 filteredArrayUsingPredicate:predicate1];
[temp1 enumerateObjectsUsingBlock:^(id  _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
NSLog(@"temp1 = %@",obj);
}];
/*
2015-11-08 10:55:19.879 NSPredicateDemo[11595:166012] obj ==5
2015-11-08 10:55:19.879 NSPredicateDemo[11595:166012] obj ==5
*/

基本語(yǔ)法

比較運(yùn)算符>,<,==,>=,<=,!=

可用于數(shù)值及字符串

#pragma mark 測(cè)試Predicate的比較功能
 - (void)testPredicateComparation{
    /*
     (1)比較運(yùn)算符>,<,==,>=,<=,!=
     可用于數(shù)值及字符串
     例：@"number > 100"
     */
    NSArray *array = [NSArray arrayWithObjects:@1,@2,@3,@4,@5,@2,@6, nil];
    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"SELF >4"];
    NSArray *fliterArray = [array filteredArrayUsingPredicate:predicate];
    [fliterArray enumerateObjectsWithOptions:NSEnumerationConcurrent usingBlock:^(id  _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
        NSLog(@"fliterArray = %@",obj);
    }];
}

范圍運(yùn)算符：IN、BETWEEN

例：@"number BETWEEN {1,5}"
@"address IN {'shanghai','beijing'}"

#pragma mark Predicate范圍運(yùn)算功能
 - (void)testPredicateRange{
    /*
     (2)范圍運(yùn)算符：IN、BETWEEN
     例：@"number BETWEEN {1,5}"
     @"address IN {'shanghai','beijing'}"
     */
    NSArray *array = [NSArray arrayWithObjects:@1,@2,@3,@4,@5,@2,@6, nil];
    //NSPredicate *predicate = [NSPredicate predicateWithFormat:@"SELF in {2,5}"]; 找到 in 的意思是array中{2,5}的元素
    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"SELF BETWEEN {2,5}"];
    NSArray *fliterArray = [array filteredArrayUsingPredicate:predicate];
    [fliterArray enumerateObjectsWithOptions:NSEnumerationConcurrent usingBlock:^(id  _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
        NSLog(@"fliterArray = %@",obj);
    }];
}

字符串本身:SELF

例：@“SELF == ‘APPLE’"

 #pragma  mark Predicate 與自身相比的功能
 - (void)testPredicateComparationToSelf{
    /*
     (3)字符串本身:SELF
     例：@“SELF == ‘APPLE’"
     */
    
    NSArray *placeArray = [NSArray arrayWithObjects:@"Shanghai",@"Hangzhou",@"Beijing",@"Macao",@"Taishan", nil];
    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"SELF == 'Beijing'"];
    NSArray *tempArray = [placeArray filteredArrayUsingPredicate:predicate];
    [tempArray enumerateObjectsUsingBlock:^(id  _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
        NSLog(@"obj == %@",obj);
    }];   
}

字符串相關(guān)：BEGINSWITH、ENDSWITH、CONTAINS

例：@"name CONTAIN[cd] 'ang'"  //包含某個(gè)字符串
@"name BEGINSWITH[c] 'sh'"    //以某個(gè)字符串開頭
@"name ENDSWITH[d] 'ang'"      //以某個(gè)字符串結(jié)束
注:[c]不區(qū)分大小寫[d]不區(qū)分發(fā)音符號(hào)即沒有重音符號(hào)[cd]既不區(qū)分大小寫，也不區(qū)分發(fā)音符號(hào)。

#pragma mark Predicate 字符串相關(guān)：BEGINSWITH、ENDSWITH、CONTAINS
 - (void)testPredicateRelateToNSString{
    /*
     (4)字符串相關(guān)：BEGINSWITH、ENDSWITH、CONTAINS
     例：@"name CONTAIN[cd] 'ang'"   //包含某個(gè)字符串
     @"name BEGINSWITH[c] 'sh'"     //以某個(gè)字符串開頭
     @"name ENDSWITH[d] 'ang'"      //以某個(gè)字符串結(jié)束
     注:[c]不區(qū)分大小寫[d]不區(qū)分發(fā)音符號(hào)即沒有重音符號(hào)[cd]既不區(qū)分大小寫，也不區(qū)分發(fā)音符號(hào)。
     */
    NSArray *placeArray = [NSArray arrayWithObjects:@"Shanghai",@"Hangzhou",@"Beijing",@"Macao",@"Taishan", nil];
    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"SELF CONTAINS [cd] 'an' "];
   // NSPredicate *predicate1 = [NSPredicate predicateWithFormat:@"SELF Beginswith [cd] 'sh' "];

    NSArray *tempArray = [placeArray filteredArrayUsingPredicate:predicate];
    [tempArray enumerateObjectsUsingBlock:^(id  _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
        NSLog(@"obj == %@",obj);
    }];   
}

通配符：LIKE

例：@"name LIKE[cd] '*er*'"    //*代表通配符,Like也接受[cd].
@"name LIKE[cd] '???er*'"

#pragma mark Predicate 的通配
 - (void)testPredicateWildcard{
    /*
     (5)通配符：LIKE
     例：@"name LIKE[cd] '*er*'"    
     //  *代表通配符,Like也接受[cd].
     @"name LIKE[cd] '???er*'"
     */
    NSArray *placeArray = [NSArray arrayWithObjects:@"Shanghai",@"Hangzhou",@"Beijing",@"Macao",@"Taishan", nil];
    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"SELF  like '*ai*' "];
    
    NSArray *tempArray = [placeArray filteredArrayUsingPredicate:predicate];
    [tempArray enumerateObjectsUsingBlock:^(id  _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
        NSLog(@"obj == %@",obj);
    }];
}

具體代碼見git：https://github.com/jiulin/NSPredicateDemo
期待和你一起學(xué)習(xí)！

原文鏈接：http://www.itdecent.cn/p/b2694972863e
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