Key-Value Observing Quick Start Case Study

1) create a console output project:

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2) Add two new classes: BankObject and PersonObject. Note that the parent class is NSObject.

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3) Add the following attributes to the BankObject header file and source file:

@property int accountBalance;

@synthesize accountBalance;

4) Add a response function to the PersonObject source file.

- (void)ob

The following prompt is displayed. Click Enter.

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5) as a Demo, We can output the modified value in this function. The NSLog statement added in this function:

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6) switch to the main. m file, add the following code, and introduce the header file.

#import "BankObject.h"#import "PersonObject.h"

Comment out the original output statement and add the following code:

BankObject * bankInstance = [[BankObject alloc] init]; PersonObject * personInstance = [[PersonObject alloc] init]; /** @ brief register the personInstance as the observer of the accountBalance attribute */[bankInstance addObserver: personInstance forKeyPath: @ "accountBalance" options: NSKeyValueObservingOptionNew context: NULL]; bankInstance. accountBalance = 100; bankInstance. accountBalance = 200; bankInstance. account balance = 300;

7) switch to the output of the PersonObject. m source file and place the breakpoint. When you run the program, the program jumps to the breakpoint,

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8) Click 650) this. width = 650; "src =" http://www.bkjia.com/uploads/allimg/131228/104HI637-7.png "title =" QQ20130828-23.png "/> to step down, the new value of the output is 100.

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Reference connection: http://www.cocoadev.cn/Objective-C/Key-Value-Observing-Quick-Start-cn.asp

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