iOS Apprentice 2.1: StoreSearch教程 - iOS7入门指南

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《iOS Apprentice 第二版：StoreSearch v2.1》是Razeware LLC出版的一本针对iOS开发者的入门教程，由Matthijs Hollemans撰写。本书旨在帮助读者理解和掌握iOS 7时代的应用开发技术，特别关注了App Store搜索功能的实现。在第二版中，作者深入剖析了如何在实际项目中构建定制的UITableViewCell，以及如何有效地利用苹果的调试工具进行应用程序调试。章节“Custom table cells in Interface Builder”介绍了如何在Interface Builder中设计和实现自定义表格视图单元格，这对于构建用户友好的界面至关重要。开发者将学习如何处理数据绑定、设置视图层次结构以及响应用户的交互，这对于UI设计和用户体验的优化具有实践指导意义。接着，章节“Ther debugger”引导读者探索和理解Xcode中的调试工具，如断点设置、内存分析和性能调优技巧。这部分内容对于解决实际开发过程中的问题，提升代码质量和性能有着不可或缺的作用。最后，“It’s all about the network”部分着重讨论了网络编程在iOS应用中的关键性，包括HTTP请求、API集成和错误处理。随着移动应用越来越依赖于互联网服务，理解网络通信的原理和最佳实践对于现代iOS开发者来说是必备技能。《iOS Apprentice 第二版：StoreSearch》不仅适合初学者系统学习iOS开发，也适合有一定基础的开发者深化对特定功能的理解和实践。版权方强调所有内容未经许可不得复制或分发，同时声明提供的书籍和源代码仅限于个人学习使用，并附带了一些免责声明，即作者和版权所有者不对软件的使用造成的任何损失或责任负责。通过阅读这本书，开发者可以提升iOS应用开发能力，尤其是在与App Store交互、用户体验设计以及网络编程方面，为职业发展打下坚实的基础。

The iOS Apprentice (Second Edition) StoreSearch

The search view controller with Search Bar and Table View

You know what’s coming next: connecting the Search Bar and the Table View to

outlets on the view controller.

! Add the following to SearchViewController.m. It goes into the class extension

at the top of the file:

@interface SearchViewController ()

@property (nonatomic, weak) IBOutlet UISearchBar *searchBar;

@property (nonatomic, weak) IBOutlet UITableView *tableView;

@end

Recall that as soon as an object no longer has any strong pointers, it goes away (it

is deallocated) and all the weak pointers become nil. Per Apple’s recommendation

you’ve been making your outlets weak pointers. You may be wondering, if the

pointers to these view objects are weak, then won’t the objects get deallocated too

soon?

Exercise. What is keeping these views from being deallocated? 

Answer: Views are always part of a view hierarchy and they will always have an

owner with a strong pointer: their superview. In this screen, the

SearchViewController’s main view object will hold a reference to both the search

bar and the table view. This is done inside UIKit and you don’t have to worry about

it. As long as the view controller exists, so will these two outlets.

The iOS Apprentice (Second Edition) StoreSearch

of the inspector area). The Custom Class field will show you the owner’s name.

If you do that for this nib, you’ll see that it says SearchViewController.

If you run the app now, you’ll notice a small problem: the first rows of the Table

View are hidden beneath the Search Bar.

That’s not so strange because in the nib you put the Search Bar on top of the table.

To fix this you could nudge the Table View down a few pixels. However, according

to the design guidelines for iOS 7 the content of a view controller should take up

the entire screen space. So it’s better to leave the size of the Table View alone and

to make the Search Bar partially translucent to let the contents of the table cells

shine through. But it would still be nice to see the first few rows in their entirety.

You can compensate for this with the content inset attributes of the Table View.

Unfortunately, with Auto Layout enabled this attribute is unavailable in Interface

Builder (at least in Xcode 5.0) so you’ll have to do this from code.

! Add the following line to viewDidLoad in SearchViewController.m:

- (void)viewDidLoad

{

[super viewDidLoad];

self.tableView.contentInset = UIEdgeInsetsMake(64, 0, 0, 0);

}

This tells the table view to add a 64-point margin at the top, made up of 20 points

for the status bar and 44 points for the Search Bar. Now the first row will always be

visible, and when you scroll the table view the cells still go under the search bar.

Nice.

Doing fake searches

Before you can search the iTunes store, it’s good to understand how the

UISearchBar component works. In this section you’ll get the text to search for from

the search bar and use that to put some fake search results into the table view.

Once you’ve got that working, you can build in the web service. Small steps!

! Run the app. If you tap in the search bar, the on-screen keyboard will appear, but

it still doesn’t do anything when you tap the Search button.

The iOS Apprentice (Second Edition) StoreSearch

That’s what this error means: SearchViewController is missing the method named

tableView:numberOfRowsInSection:.

Whenever you get the “unrecognized selector” error, you forgot to implement a

method somewhere (or you may have misspelled it). Fortunately, the error

message also tells you which object is missing the method, and what the method

name is supposed to be.

! Add the following to the bottom of SearchViewController.m:

#pragma mark - UITableViewDataSource

- (NSInteger)tableView:(UITableView *)tableView

numberOfRowsInSection:(NSInteger)section

{

return 0;

}

- (UITableViewCell *)tableView:(UITableView *)tableView

cellForRowAtIndexPath:(NSIndexPath *)indexPath

{

return nil;

}

This simply tells the table view that it has no rows yet. Soon you’ll give it some fake

data to display, but for now you just want to be able to run the app without the

table view crashing.

Often you can declare to conform to a protocol without implementing any of its

methods. This works fine for UISearchBarDelegate, for example, but obviously not in

the case of UITableViewDataSource! A protocol can have @optional and @required

methods and if you forget a required method, a crash is your reward. Fortunately,

Xcode already warns about any missing delegate methods when you build the app.

As always, pay attention to the warnings from Xcode!

! Run the app. It should no longer crash.

The UISearchBarDelegate protocol has a method searchBarSearchButtonClicked:

that is invoked when the user taps the Search button on the keyboard. You will

implement this method to put some fake data into the table. In a little while you’ll

make this method send a network request to the iTunes store to find songs, movies

and ebooks that match the search text that the user typed, but let’s not do too

many new things at once!

! Add the following method to SearchViewController.m, below the table view

stuff:

#pragma mark - UISearchBarDelegate

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