Question

-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event{

UITouch *touch = [touches anyObject];
CGPoint location = [touch locationInNode:self];
SKNode *node = [self nodeAtPoint:location];

if ([node.name isEqualToString:@"play"]){

    NSLog(@"play was touched");

    SKScene *mainGameScene = [[MainGame alloc] initWithSize:self.size];
    if (!mainGameScene){
    SKTransition *transition = [SKTransition fadeWithColor:[UIColor blackColor] duration:0.5];
    [self.view presentScene:mainGameScene transition:transition];
    }

}

}

根据我的理解，上面的代码检查mainGameScene是否为零，如果是，则通过if语句。

这是否有益或者只是浪费代码，因为如果此代码所在的方法多次调用，则会创建SKScene的新对象？

Answer 1

用于检查mainGameScene是否已初始化，因为如果presentScene，则nil不能SKScene *mainGameScene; //creates new variable - place it at the beginning of the code, before @implementation and @interface if(mainGameScene){ // it is already inited (you have already tapped once), it will be called always, since it is inited at else //it is called when you tap the second, the third time, etcetera SKTransition *transition = [SKTransition fadeWithColor:[UIColor blackColor] duration:0.5]; [self.view presentScene:mainGameScene transition:transition]; }else { //Calls only once, when you first touching the screen, and initing mainGameScene. //It won't be called ANYMORE, since it is inited. mainGameScene = [[MainGame alloc] initWithSize:self.size]; }。如果你只想检查对象是否被初始化，那么

mainGameScene

你现在拥有的代码是无用的，因为它试图用对象做一些事情，但是没有初始化。
就我而言，你的{{1}}不会被重新初始化，一旦它被引入。

测试如果对象是否为零

1 个答案: