oc 谓词

 NSPredicate 作用：筛选

常用于：

1、加条件筛选数组中的符合谓词的对象 

 + (NSPredicate *)predicateWithFormat:(NSString *)predicateFormat, ...; 设定谓词过滤条件

- (NSArray *)filteredArrayUsingPredicate:(NSPredicate *)predicate; 数组调用谓词进行过滤

2、用一个设定条件的谓词评估是否一个对象符合该谓词

- (BOOL)evaluateWithObject:(id)object  

 

Student *chuxiao = [[Student alloc]init];
         Student *panxiaoliang = [[Student alloc]init];
         Student *lizhenggeng = [[Student alloc]init];
        
        [chuxiao info1];
        [panxiaoliang info2];
        [lizhenggeng info3];
       
        NSArray *arr = [[NSArray alloc]initWithObjects:chuxiao,panxiaoliang,lizhenggeng, nil];
       
        
        NSPredicate *stuPredicate1 = [NSPredicate predicateWithFormat:@"name beginsWith 'p'"];
        NSArray *arr1 = [arr filteredArrayUsingPredicate:stuPredicate1];
        NSLog(@"name beginsWith 'p':%@",arr1);
        
        NSPredicate *stuPredicate2 = [NSPredicate predicateWithFormat:@"studentID = 1"];
        NSArray *arr2 = [arr filteredArrayUsingPredicate:stuPredicate2];
        NSLog(@"studentID = 1:%@",arr2);
        
        NSPredicate *stuPredicate3 = [NSPredicate predicateWithFormat:@"name = 'lizhenggeng'"];
        NSArray *arr3 = [arr filteredArrayUsingPredicate:stuPredicate3];
        NSLog(@"name = 'lizhenggeng':%@",arr3);
        
        NSPredicate *stuPredicate4 = [NSPredicate predicateWithFormat:@"name like 'l*'"];
        NSArray *arr4 = [arr filteredArrayUsingPredicate:stuPredicate4];
        if(arr4.count == 0)
        {
            NSLog(@"name like 'l*' not found!");
        }
        else NSLog(@"name like 'l*':%@",arr4);
        
        NSPredicate *mathRange80_90 = [NSPredicate predicateWithFormat:@"math >= 80 && math <= 90"];
        BOOL isIn = [mathRange80_90 evaluateWithObject:panxiaoliang];
        if(isIn)
        {
            NSLog(@"panxiaoliang's MathScore is between 80 and 90");
        }
        else NSLog(@"out of the range");