Question

//在Xcode 4.2中打开了ARC

创建一个静态函数，它执行查询并从数据库SQLite中获取值。函数displayquery返回的数组值是包含记录的no可变数组的数组。我想将它转换为客户端对象，并在返回之前将列表列表存储在NSMutable对象中。

静态功能

+ (NSMutableArray*) list
{

    NSString *querySQL = //some query;

    NSMutableArray *values = [Client displayQuery:querySQL numberOfColumns:7];

    NSMutableArray *lst = nil;

    if (values != nil)
    {
        lst = [NSMutableArray arrayWithObject:@"Client"];

        for (int i = 0; i<[[values objectAtIndex:0] count] ; i++) 
        {    
            [lst addObject:[Client new ]];
        }
        for (int i = 0; i<[[values objectAtIndex:0] count] ; i++) 
        {    

            Client *aClient = [lst objectAtIndex:i];
            //error occurs during the execution of this line.
            //all properties of Class client are (retain,nonatomic)
            aClient.idClient = [[values objectAtIndex:0]objectAtIndex:i];
            aClient.prenom = [[values objectAtIndex:1]objectAtIndex:i];
            aClient.name = [[values objectAtIndex:2]objectAtIndex:i];
            aClient.address = [[values objectAtIndex:3]objectAtIndex:i];
            aClient.telephone = [[values objectAtIndex:4]objectAtIndex:i];
            aClient.email = [[values objectAtIndex:5]objectAtIndex:i];
            aClient.weight = [[values objectAtIndex:6]objectAtIndex:i];
            [lst addObject: aClient];

        }
    }
    return lst;
}

Answer 1

问题是，lst数组中的第一个元素是NSString，它没有Client类所具有的任何属性，并且当您尝试分配时对它来说，你得到一个错误。您的代码中存在一些问题：

不要将@"Client"添加为数组中的元素，因为它似乎不属于那里。
您无需将Client个对象“预先添加”到数组中。只需创建它们并随时将它们添加到阵列中。
当您拥有数组数组时，查找项目时可能会更难理解每个索引的用途。我在代码中重命名了几个变量，因为它让我更容易理解。

我认为您的代码应该更像这样：

+ (NSMutableArray*) list
{
    NSString *querySQL = //some query;
    NSMutableArray *columns = [Client displayQuery:querySQL numberOfColumns:7];
    NSMutableArray *lst = nil;

    if (columns == nil)
        return nil;

    NSUInteger count = [[columns objectAtIndex:0] count];
    lst = [NSMutableArray arrayWithCapacity:count];

    for (NSUInteger row = 0; row < count; row++) 
    {    
        Client *aClient = [Client new];

        aClient.idClient = [[columns objectAtIndex:0] objectAtIndex:row];
        aClient.prenom = [[columns objectAtIndex:1] objectAtIndex:row];
        aClient.name = [[columns objectAtIndex:2] objectAtIndex:row];
        aClient.address = [[columns objectAtIndex:3] objectAtIndex:row];
        aClient.telephone = [[columns objectAtIndex:4] objectAtIndex:row];
        aClient.email = [[columns objectAtIndex:5] objectAtIndex:row];
        aClient.weight = [[columns objectAtIndex:6] objectAtIndex:row];

        [lst addObject: aClient];
    }

    return lst;
}

NSMutableArray中的对象不可用Objective-C

1 个答案: