UILocalizedIndexedCollat​​ion的sectionForObject:(id)object collat​​ionStringSelector:(SEL)selector方法中选择器的作用是什么 [英] What is the role of selector in UILocalizedIndexedCollation's sectionForObject:(id)object collationStringSelector:(SEL)selector method

问题描述

我是iOS开发的初学者，正在经历

I am a beginner of iOS development and while going through this document (iOS Developer Guide about configuring a TableView with Indexed List) I came across this:

// Listing 4.7
for (State *theState in statesTemp) {
        NSInteger sect = [theCollation sectionForObject:theState collationStringSelector:@selector(name)];
        theState.sectionNumber = sect;
    }

我无法确定选择器(@selector(name))及其用途，也无法找到在选择器中传递名称的方法，即name.我搜索了一些示例以找到更好的解释，并遇到了此示例.

I could not figure out the selector (@selector(name)) and its purpose, nor could I find the method with the name passed in the selector i.e. name. I googled for examples to find a better explanation, and came across this example.

在代码清单中，有一条语句是方法调用:

In the code listing, there is a statement which is a method call:     

self.tableData = [self partitionObjects:objects collationStringSelector:@selector(title)];

现在选择器称为title.我找不到更好的解释，我的问题是此选择器的目的是什么以及该选择器引用的方法，它应该做什么并返回.

now the selector is called title. I have not been able to find a better explanation, and my question is what is the purpose of this selector and the method referred by this selector, and what should it do and return.

推荐答案

一般

使用@selector(title:)定义将调用的方法.

In general

With the @selector(title:) you define which method will be called.

在我的示例中，它将调用

in my example it will call

- (void) title:(id)someObject {}

最后请小心用分号！如果最后使用分号，则您的方法将具有上面类似我的参数.

Be carefull with the semicolon at the end! If you have a semicolon at the end you method will have parameters like mine above.

您的代码仅声明了@selector(title)，并且将调用不带参数的方法标题，如下所示:

Your code states just @selector(title) and will call a method title without a parameter like this:

- (void)title {}

特定于UILocalizedIndexCollat​​ion

文档状态:

Specific to UILocalizedIndexCollation

The docs state:

选择器
选择器，用于标识返回标识的方法 排序规则中使用的对象的字符串.该方法不应该 参数并返回一个NSString对象.例如，这可能是 对象的名称属性.

selector
A selector that identifies a method returning an identifying string for object that is used in collation. The method should take no arguments and return an NSString object. For example, this could be a name property on the object.

所以我建议您像这样实现它

So i would suggest you implement it like this

self.tableData = [self partitionObjects:objects collationStringSelector:@selector(title)];
 ...
- (NSString *)title {
     NSString *title;
     // some code to fill title with an identifier for your object
     return title;
}

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