NSPredicate 帮助计算数组中的对象

Question

我有一个包含字典的数组，我想根据每个字典中的“名称”字段在表视图中显示值。假设名称以“a”开头；那么“b”和“c”位于不同的部分。部分的数量对应于词典的“名称”字段。如何获取行数？如果有人知道请给出解决方案。

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {

    //---get the letter in each section; e.g., A, B, C, etc.---
    NSString *alphabet = [subscribeIndexArray objectAtIndex:section];

    //---get all states beginning with the letter---

    //NSMutableArray *states =[[NSMutableArray alloc]init];
    NSArray *states;
    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"SELF beginswith[c] %@", alphabet];

    for(NSDictionary *dict in subscribeViewArray1)
    {
       states =[[dict valueForKey:@"name"] filteredArrayUsingPredicate:predicate];
    }

    //---return the number of states beginning with the letter---
    return [states count];
}

Answer 1

您需要将状态名称放入数组中，以便使用谓词过滤它们。

试试这个：

...
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"SELF beginswith[c] %@", alphabet];
NSMutableArray *matchingStatesArray = [[NSMutableArray alloc] init];
for (NSDictionary *dict in subscribeViewArray1) {
       //get the state names in an array
    [matchingStatesArray addObject:[dict objectForKey:@"name"]];
    }
    [matchingStatesArray filterUsingPredicate:predicate];

    return [[matchingStatesArray autorelease] count];
}