Cocoa框架中的NSPredicate用于查询

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

  • pragma mark Predicate 的通配

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    - (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);
    }];
  • pragma mark Predicate 字符串相关:BEGINSWITH、ENDSWITH、CONTAINS

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    - (void)testPredicateRelateToNSString{
    / (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。
    /
    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);
    }];
    }
  • pragma mark Predicate 与自身相比的功能

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    - (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);
    }];
    }
  • pragma mark Predicate范围运算功能

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    - (void)testPredicateRange{
    /
    (2)范围运算符:IN、BETWEEN
    例:@"number BETWEEN {1,5}"
    @"address IN {'shanghai','beijing'}"
    /
    // NSArray array = [NSArray arrayWithObjects:@1,@2,@3,@4,@5,@2,@6, nil];
    NSArray array = [NSArray arrayWithObjects:@"shanghai",@"beijing", 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);
    }];
    }
  • pragma mark 测试Predicate的比较功能

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    - (void)testPredicateComparation{
    /
    (1)比较运算符>,<,==,>=,<=,!=
    可用于数值及字符串
    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);
    }];
    }