Question

我似乎无法将数据保存到AppDelegate中的自定义实例对象。我的自定义类非常简单，如下所示：

Person.h

...
@interface Person : NSObject {
    int _age;
}

- (void) setAge: (int) age;
- (int) age;
@end

Person.m

#import "Person.h"

@implementation Person

- (void) setAge:(int) age {
    _age = age;
}
- (int) age {
    return _age;
}
@end

然后我在AppDelegate类中创建了一个Person实例：

AppDelegate.h

@class Person;

@interface AccuTaxAppDelegate : NSObject <UIApplicationDelegate> {
    ...
Person *person;
}
...
@property (nonatomic, retain) Person *person;
@end

AppDelegate.m

...
#import "Person.h"

@implementation AccuTaxAppDelegate

...
@synthesize person;

- (void)applicationDidFinishLaunching:(UIApplication *)application {

    // Override point for customization after app launch    
    [window addSubview:[navigationController view]];
    [window makeKeyAndVisible];
}

- (void)applicationWillTerminate:(UIApplication *)application {
// Save data if appropriate
}

#pragma mark -
#pragma mark Memory management

- (void)dealloc {
    [navigationController release];
    [window release];
    [person release];
    [super dealloc];
}
@end

最后，在我的ViewController代码中，我抓住AppDelegate上的一个句柄，然后抓住person实例，但是当我尝试保存年龄时它似乎不起作用：

MyViewController

...
- (void)textFieldDidEndEditing:(UITextField *)textField
{
    NSString *textAge = [textField text];
    int age = [textAge intValue];
    NSLog(@"Age from text field::%i", age);

    AppDelegate *appDelegate = 
        (AppDelegate *)[UIApplication sharedApplication].delegate;

    Person *myPerson = (Person *)[appDelegate person];
    NSLog(@"Age before setting: %i", [myPerson age]);
    [myPerson setAge:age];
    NSLog(@"Age after setting: %i", [myPerson age]);

    [textAge release];
}
...

上述NSLog的输出为：

[Session started at 2010-05-04 18:29:22 +0100.]
2010-05-04 18:29:28.260 AccuTax[16235:207] Age in text field:25
2010-05-04 18:29:28.262 AccuTax[16235:207] Age before setting: 0
2010-05-04 18:29:28.263 AccuTax[16235:207] Age after setting: 0

为什么'年龄'没有被存储的任何想法？我对Obj-C比较陌生，所以如果我错过了一些非常简单的话，请原谅我！

Answer 1

看起来你从未真正创建过Person的实例 - 在AccuTaxAppDelegate中添加一个包含该行的init方法

person = [[Person alloc] init];

否则人是零;

通过AppDelegate在自定义类中保存数据

1 个答案: