iOS基础知识：Objective-C 之 谓词

谓词

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思维导图

这里先建个类Person，以下都是基于这个类解说

@interface Person : NSObject

@property (nonatomic,copy) NSString *name;
@property (nonatomic,assign) NSUInteger age;
@property (nonatomic,copy) NSString *gender;
@property (nonatomic,strong) NSArray *skills;

@end
@implementation Person

 + (instancetype)personWithName:(NSString *)name age:(NSUInteger)age gender:(NSString *)gender{
    Person *p = [[Person alloc]init];
    p.name = name;
    p.age = age;
    p.gender = gender;
    return p;
}
@end

• 单条件判断（数字、字符串）
  数字相等判断

    Person *p = [Person personWithName:@"Geroge" age:20 gender:@"male"];

    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"age == 20"];
    if ([predicate evaluateWithObject:p]) {
        NSLog(@"YES");
    }else{
        NSLog(@"NO");
    }

字符串判断

    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"name in {'Geroge'}"];

数值在某个范围内判断

    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"age between {18,22}"];

• 多条件判断 （与或非）
  name为Geroge 并且 age等于20

    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"name in {'Geroge'} AND age == 20"];

name为Geroge或者age等于20

    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"name in {'Geroge'} OR age == 20"];

age不为20

    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"not age == 20"];

• 不定向条件判断 （开头，结尾，包含，匹配）
  name 以 Ger 开头判断

    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"name beginswith 'Ger'"];

name 以 ge 结尾判断

    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"name endswith 'ge'"];

name 包含 rog 判断

    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"name contains 'rog'"];

name 中是否有 Ger*匹配

    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"name like 'Ger*'"];

• 判断集合属性是否含有某元素
  如果设置skills属性，既加入一个数组，检查数组内是否有某类对象

    p.skills = @[@"hello",@"world",@"yes",@"no"];
    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"any skills like 'ye*'"];

判断是否全部都有某种属性

    p.skills = @[@"hello",@"world",@"yes",@"no"];
    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"all skills like 'ye*'"];

判断是否没有该属性

    p.skills = @[@"hello",@"world",@"yes",@"no"];
    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"none skills like 'ye*'"];

• 格式化谓词
  格式化path 用 %K,此处K必须大写

    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"any %K like '*e*l*o'",@"skills"];

格式化value用%@

    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"any %K like %@",@"skills",@"*e*l*o"];

self的应用

    NSString *str = @"hello world";
    predicate = [NSPredicate predicateWithFormat:@"self beginswith %@",@"he"];

• 谓词的应用
  在谓词的头文件中，加了array,dictionary,set的类别，根据所给定的predicate来过滤里面的元素，以数组为例
  先创建5个Person对象，放到数组中

    Person *p1 = [Person personWithName:@"Geroge" age:20 gender:@"male"];
    Person *p2 = [Person personWithName:@"Amy" age:18 gender:@"female"];
    Person *p3 = [Person personWithName:@"Tom" age:24 gender:@"male"];
    Person *p4 = [Person personWithName:@"Andy" age:22 gender:@"male"];
    Person *p5 = [Person personWithName:@"Rose" age:25 gender:@"female"];

    NSArray *personArray = @[p1,p2,p3,p4,p5];

如果我们想把女性留下，男性都过滤掉，可做如下操作

    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"%K like %@",@"gender",@"fe*"];
    NSArray *newArray = [personArray filteredArrayUsingPredicate:predicate];

最终中，newArray中保留的是女性的Person成员数组