Objective-C 基本类相关问题，使用类文件保留特定对象的值

Question

成员、学者、代码大师。 我的背景远离任何计算机编程，因此我的问题对您来说可能看起来很基本并且有点微不足道。尽管如此，我似乎无法理解它。 我用谷歌搜索并寻找答案，只是让自己更加困惑。 因此，我恳请您提供一个适合像我这样的非技术人员以及其他类似的人的简单解释。

我在下面留下了一条评论，文字为“这就是问题”，指的是我的问题。

//  character.h
#import <Foundation/Foundation.h>

@interface character : NSObject {
    NSString *name;
    int hitPoints;
    int armorClass;
}

@property (nonatomic,retain) NSString *name;
@property int hitPoints,armorClass;

-(void)giveCharacterInfo;

@end


//  character.m
#import "character.h"


@implementation character
@synthesize name,hitPoints,armorClass;

-(void)giveCharacterInfo{
    NSLog(@"name:%@ HP:%i AC:%i",name,hitPoints,armorClass);
}
@end



//  ClassAtLastViewController.h
#import <UIKit/UIKit.h>

@interface ClassAtLastViewController : UIViewController {

}

-(void)callAgain;

@end



//  ClassAtLastViewController.m
#import "ClassAtLastViewController.h"
#import "character.h"

@implementation ClassAtLastViewController


- (void)viewDidLoad {
    //[super viewDidLoad];
    character *player = [[character alloc]init];
    player.name = @"Minsc";
    player.hitPoints = 140;
    player.armorClass = 10;
    [player giveCharacterInfo];
    [player release];
        // Up until here, All peachy!
    [self performSelector:@selector(callAgain) withObject:nil afterDelay:2.0];
}

-(void)callAgain{
    // Here is the issue, I assume that since I init the player again I loss everything
    // Q1. I loss all the data I set above, where is it than? 
    // Q2. What is the proper way to implement this

    character *player = [[character alloc]init];
    [player giveCharacterInfo];
}

预先非常感谢，请记住，我的背景与鲑鱼育种比与计算机代码更相关，如果对您来说都一样，请尝试将您的答案降低到我的水平。

Answer 1

我丢失了上面设置的所有数据，它在哪里？

它已被释放（释放）。注意：

character *player = [[character alloc]init];    // You create the character here...
// And then you initialize it...
// Then later...
[player release];                               // You release it.

即使你没有释放它，你仍然无法从 callAgain 访问它，因为你在 viewDidLoad 中声明了 player >。如果您希望它可用于 ClassAtLastViewController 实例中的所有方法，则应将其设为实例变量。

实现这个的正确方法是什么

我不知道你的使用细节，但我想你想要这样的东西：

@interface ClassAtLastViewController : UIViewController {
    character *player;    // Make player an instance variable
}

-(void)callAgain;

@end

@implementation ClassAtLastViewController


- (void)viewDidLoad {
    //[super viewDidLoad];
    player = [[character alloc]init];    // Initialize the instance variable
    player.name = @"Minsc";
    player.hitPoints = 140;
    player.armorClass = 10;
    [player giveCharacterInfo];
    [self performSelector:@selector(callAgain) withObject:nil afterDelay:2.0];
}

-(void)callAgain{
    [player giveCharacterInfo];
}

Answer 2

当您在 callAgain 函数中初始化角色时，您实际上是在创建角色的第二个实例。尽管 callAgain 中创建的角色与 viewDidLoad 中创建的角色具有相同的名称，但它是一个完全独立的变量。你在viewDidLoad中初始化的字符只存在于viewDidLoad函数的范围内。

另外，当您在 viewDidLoad 中调用 [player release] 时，您将从内存中删除该角色实例。

我认为您想要做的是创建一个可以在整个类中使用的实例变量：

//  ClassAtLastViewController.h
#import <UIKit/UIKit.h>

@interface ClassAtLastViewController : UIViewController {
    character *player;
}

-(void)callAgain;

@end



//  ClassAtLastViewController.m
#import "ClassAtLastViewController.h"
#import "character.h"

@implementation ClassAtLastViewController


- (void)viewDidLoad {
    //[super viewDidLoad];
    player = [[character alloc]init];
    player.name = @"Minsc";
    player.hitPoints = 140;
    player.armorClass = 10;
    [player giveCharacterInfo];

    [self performSelector:@selector(callAgain) withObject:nil afterDelay:2.0];
}

-(void)callAgain{
    // Here is the issue, I assume that since I init the player again I loss everything
    // Q1. I loss all the data I set above, where is it than? 
    // Q2. What is the proper way to implement this

    [player giveCharacterInfo];
}