iphone - 需要帮助了解NSDictionary对象

Question

我试图把我的头缠在NSDictionary类上，以使TableView正常运行。
有谁能够分解并解释以下代码中发生的事情？干杯

if (!self.tableDataSource)
    {
        self.tableDataSource = [NSArray arrayWithContentsOfFile: [[NSBundle mainBundle] pathForResource: @"MenuData" ofType: @"plist"]];
        self.navigationItem.title = @"Menu";

    } 

NSDictionary *dictionary = [[[self.tableDataSource objectAtIndex: indexPath.section] objectForKey: @"Children"] objectAtIndex: indexPath.row];

Answer 1

我认为，如果只是解压缩所有方法调用以查看各种对象的隐式嵌套，代码本身就很清楚。评论:

// if the current object's tableDataSource property has not been defined yet
if (!self.tableDataSource) {
    // then define it.

    // Set it to be an NSArray initialized by reading ...
    self.tableDataSource = [NSArray arrayWithContentsOfFile: 
    // ... the plist file MenuData.plist found within the application's bundle
                      [[NSBundle mainBundle] pathForResource: @"MenuData" ofType: @"plist"]];

    // and also set the current object's property nagitationItem.title to "Menu"
    self.navigationItem.title = @"Menu";

} 

// Now create a dictionary

// Get this dictionary by ...

// going to the element numbered indexPath.section in the tableDataSource
NSDictionary *dictionary = [[[self.tableDataSource objectAtIndex: indexPath.section] 
                  // (assume that element is an NSDictionary)
                  // get that element's value stored witht the key "Children"
                  objectForKey: @"Children"] 
                 // (assume that retrieved value is an NSArray)
                 // then get the element numbered indexPath.row from that array
                 objectAtIndex: indexPath.row];
                             // expect that value to be an NSDictionary

我认为 TableDataSource上的Apple文档可能会为您提供有关此代码正在执行的操作的更大范围。特别是，将字典嵌套在数组中，在字典中，在数组中(这是最后一行的内容)可能是对行，列等所有信息进行编码的标准方法，数据驱动UITableView。