Implementing the IOS Memory Detection Tool

Memory leaks are a common problem in iOS development, where common memory detection methods are sorted out. a static detection method

Using the Xcode analysis feature, Product->analyze

Using static detection, you can check out some obvious memory that is not freed, including memory leaks at the beginning of nsobject and CF.

Disadvantage: Unable to detect block-caused memory leak problem

two dynamic detection method

Using instruments

three dealloc re-test

Rewrite the Dealloc method, when the interface returns or the object is destroyed, to determine whether to call the

Four third-party detection methods

Mlleaksfinder

Mainly examines the UI aspect the leakage, the integration is simple, the merit is as follows:
1. Different from the instrument analysis function, need manual observation, this tool automatic detection, found that there is leakage can be real-time prompt, although mainly for the UI, but for general engineering, memory leaks in the scene or the majority of the UI, so can solve a large part of the problem.
2. Memory leaks can be easily detected during the development of new features and the process of resolving bugs.

The principle is as follows: (1) detect whether the Viewcontroller has been released after the pop
(2) Set the flag bit to No in viewwillappear
(3) Set the flag bit to Yes after navgation pop
(4) To judge the mark position in the Viewdiddisappear

Based on this principle, we simply implement a simple memory detection tool of our own:

(1) exchanging the viewwillappear and viewdiddisappear of Viewcontroller with runtime technology;

(2) in Viewwillappear to set the flag to NO, the code is as follows:

-(void) Sw_viewwillappear: (BOOL) animated{
    [self sw_viewwillappear:animated];
    
    Objc_setassociatedobject (self, &kleakmemory, @ (NO), objc_association_retain_nonatomic);
}

(3) Exchange Navigationcontroller popviewcontrolleranimated, and in which the flag bit is set to Yes

-(Nullable Uiviewcontroller *) sw_popviewcontrolleranimated: (BOOL) animated{
    uiviewcontroller *VC = [Self sw_ Popviewcontrolleranimated:animated];
    
    extern const char *kleakmemory;
    Objc_setassociatedobject (self, &kleakmemory, @ (YES), objc_association_retain_nonatomic);
    
    return VC;
}

(4) To judge the mark bit in the viewdiddisappear of Viewcontroller, and to detect whether Dealloc calls

-(void) Sw_viewdiddisappear: (BOOL) animated{[self sw_viewdiddisappear:animated];
    if (Objc_getassociatedobject (self, &kleakmemory)) {[Self willdealloc]; }}-(BOOL) Willdealloc {if (![
    Super Willdealloc]) {return NO;
return YES; }

/**super willdealloc*/
-(BOOL) willdealloc{
    ///Here Note that using weakself prevents circular references
    __weak typeof (self) weakself =  self;
    Dispatch_after (Dispatch_time (Dispatch_time_now, (int64_t) (2 * nsec_per_sec)), Dispatch_get_main_queue (), ^{
        __ Strong typeof (Weakself) strongself = weakself;
        [Strongself Showmsg:nsstringfromclass ([Strongself class])];
    Return YES
}

-(void) ShowMsg: (NSString *) msg{
    Uialertview *alertviewtemp = [[Uialertview alloc] initwithtitle:@ "Leak"
                                                            Message:msg
                                                           delegate:nil
                                                  cancelbuttontitle:@ "OK"
                                                  Otherbuttontitles:nil];
    [Alertviewtemp show];
}

Demo

If you have questions, you are welcome to point out.