iOS 之谓词 NSPredicate

Person *person1 = [Person new]; person1.age = @21; person1.lastname = @"zhang"; person1.firstname = @"san"; Person *person2 = [Person new]; person2.age = @25; person2.lastname = @"li"; person2.firstname = @"si"; Person *person3 = [Person new]; person3.age = @31; person3.lastname = @"wang"; person3.firstname = @"wu";
Person *person4 = [Person new]; person4.age = @35; person4.lastname = @"zhao"; person4.firstname = @"liu"; Person *person5 = [Person new]; person5.age = @41; person5.lastname = @"test"; person5.firstname = @"san";

//创建谓词的对象谓词条件是基于KVC的， NSPredicate* predicate = [NSPredicate predicateWithFormat:@"lastname=‘wang‘ AND firstname==‘wu‘"]; for(Person * person in personArray) { if([predicate evaluateWithObject: person]) { NSLog(@" person.lastname = %@",person.lastname); } }

NSArray *arrays = [NSArray arrayWithObjects: @"JK_RUI", @"KERP", @"SOFT", nil]; NSPredicate *predicate = [NSPredicate predicateWithFormat:@"SELF==‘SOFT‘"]; NSArray *resultArr = [arrays filteredArrayUsingPredicate:predicate]; for (NSString *tempStr in resultArr) { NSLog(@"tempStr = %@", tempStr); }

NSArray* array = @[@"apple",@"iPhone"]; NSArray* array2 = @[@"apple",@"iPhone",@"ipad",@"mac"]; NSPredicate* thePredicate = [NSPredicate predicateWithFormat:@"NOT(SELF in %@)",array]; NSArray* arr3 = [array2 filteredArrayUsingPredicate:thePredicate]; NSLog(@"arr3=%@",arr3);

NSString *regex = @"^A.+e$";//以A 开头，以e 结尾的字符。 NSPredicate *pre = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", regex]; if([pre evaluateWithObject: @"Apple"]){ printf("YES\n"); }else{ printf("NO\n"); }

1、动态属性名

假设你的代码如下

NSPredicate *p = [NSPredicate predicateWithFormat:@"name = %@", @"name1"];

显然代码没有任何问题，但是这个不是最好的写法我建议如下写法：

NSPredicate *preTemplate = [NSPredicate predicateWithFormat:@"name==$NAME"];
NSDictionary *dic=[NSDictionary dictionaryWithObjectsAndKeys:
@"name1", @"NAME",nil];
NSPredicate *pre=[preTemplate predicateWithSubstitutionVariables: dic];

这样看上去可能会让代码逻辑更清晰。

2、当过滤条件字段都是动态的时候

    NSString *key = @"name";
    NSString *value = @"name1";
    NSPredicate *p = [NSPredicate predicateWithFormat:@"%@ = %@", key, value];

然后当你执行到第三行的时候代码就会报错！
逻辑上没错误啊！！！为什么会出错呢？
NSPredicate要自动添加引号，所以最后得到的格式应该是@"‘name‘ = ‘name1‘"。明显不对。要做的就是:

NSPredicate *p = [NSPredicate predicateWithFormat:@"%K = %@", key, value];

总结：

NSPredicate的简单的使用就介绍到这里，这里有些都是从网络上或者是其他的博客上看到的，以后有新的需求再进行完善。