How to free memory when iOS receives a system memory warning

-(void) didreceivememorywarning{    [Super didreceivememorywarning];    if (_userinfoviewctl! = Nil && [_userinfoviewctl isviewloaded]) {        if (_userinfoviewctl.view.window = = nil) { C4/>self.userinfoviewctl = nil;}}}    

　　

-(Keuserinfoviewcontroller *) userinfoviewctl{    if (!_userinfoviewctl) {        _userinfoviewctl = [[ Keuserinfoviewcontroller alloc] init];    }    return _userinfoviewctl;}

　　

Note the use of _userinfoviewctl and Self.userinfoviewctl

The reason for this is the lazy loading of the property, and if _userinfoviewctl.view.window uses Self.userInfoViewCtl.view.window here, then this value will never be nil, because it will be created every time.

How to free memory when iOS receives a system memory warning