ios – 为什么两个init函数都被调用

@interface myView：UIView

- (id)init {
    self = [super init];
    if(self){
        [self foo];
    }
    return self;
}

- (id)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self) {
        // Initialization code
        [self foo];
    }
    return self;
}


-(void) foo{
   //Build UIView here 
}

为什么我会使用foo两次

@H_148_9@myView *aView = [[myView alloc]init]];

要么

@H_148_9@myView *aView = [[myView alloc]initWithFram:aFrame];