Question

我的方法中有一个View对象突然变为零。

我没有使用ARC

不涉及线程

发生的事情是，我第一次称 1stmethod 方法一切正常，并且保留了对livescoreSettings的引用。

接下来当我调用 2ndmethod 方法时，livescoreSettings ref也会被保留，但是当委托方法被激活时，该变量的引用就会丢失..不知道为什么......

@interface XY {
    LiveScoreSettingsView * livescoreSettings; // initialisation in .h file inside    
}
@end

@implementation

// 1st method
- (void)1stmethod:(id) callingClass username:(NSString*)username {
    livescoreSettings=callingClass;   // retain count increases to 1 
    isLivescoresSettingsView = YES;

    //.... some code where the above livescoreSettings variables are not used ... //
}

// 2nd method  
- (void)2ndmethod:(id) callingClass username:(NSString*)username matchid:(NSString *)matchid  eventType:(NSString *) eventType  add:(NSString *) add {
    livescoreSettings=callingClass;
    isLivescoresSettingsView = YES;
    addEventToList = YES;

    //.... some code where the above livescoreSettings variables are not used ... //
}

// delegate method thats activated when the response comes 
- (BOOL)xmppStream:(XMPPStream *)sender didReceiveIQ:(XMPPIQ *)iq {
   // the block where the data is sent to a particular view to reload table 
   else if(isLivescoresSettingsView== YES || addEventToList == YES) {
    isLivescoresSettingsView=NO;
    addEventToList = NO;

     //.... some code where the above livescoreSettings variables are not used ... //

    if(success)
        NSLog(@"No Errors with retain count = %d ", [livescoreSettings retainCount]); 
    else
        NSLog(@"Error Error Error!!!");

    [livescoreSettings.tableView reloadData];

   // when **2ndmethod** is called there's no memory reference to  livescoreSettings, tableView delegate methods are not called which is obvious. But not sure why the retain count is reducing abruptly.
    }
}

@end

Answer 1

问题是，您没有将livescoreSetting的所有权转移到1stmethod或2ndmethod。如果您不使用ARC，那么您需要retain使用这些方法，release使用dealloc方法（只需将实例分配给livescoreSetting 不使用MRR时增加保留计数。）

想象一下，如果以这种方式调用1stmethod：

LivescoreSettingsView *view = [[LivescoreSettingsView alloc] init];
[whateverItsCalled 1stmethod:view;         // (1)
[view release];                            // (2)

然后在{1}处将view分配给whateverItsCalled.livescoreSetting，但保留计数为1.在（2）保留计数为0之后，whateverItsCalled.livescoreSetting现在是悬空指针，我很惊讶你没有看到“发送到解除分配对象的消息”等消息，而不是你看到的错误（我不明白为什么当没有参与ARC时它被分配给nil。）

要解决此问题，您需要synthesize实例变量的setter / getter方法，为其添加@property。我更喜欢使用前导下划线（_）命名实例变量，以区别于setter / getter方法名称;这样：

.h文件：

@interface WhateverItsCalled : NSObject
{
    LiveScoreSettingsView *_livescoreSetting;
}

@property (retain, nonatomic, readwrite) LiveScoreSettingsView *livescoreSetting;

.m文件：

@implementation WhateverItsCalled
@synthesize livescoreSetting = _livescoreSetting;

- (void)dealloc
{
    self.livescoreSetting = nil;           // Release the object by assigning nil
    [super dealloc];
}

- (void)firstmethod:(id) callingClass username:(NSString*)username
{
    self.livescoreSettings = callingClass;   // Note the use of self!
    isLivescoresSettingsView = YES;
}

- (void)secondmethod:(id)callingClass username:(NSString*)username matchid:(NSString *) matchid  eventType:(NSString *) eventType  add:(NSString *) add

{
    self.livescoreSettings = callingClass;   // Note the use of self!
    isLivescoresSettingsView = YES;
    addEventToList = YES;
}

查看对象突然变为零 - xcode

1 个答案: