按钮点击--圆形UIButton圆形点击范围

• 判定触摸点是否在圆形范围之内

本例所实现的判定机制采用的是基本的几何运算，也就是检查触摸点是不是在圆形的半径之内

- (BOOL)pointInside:(CGPoint)point withEvent:(UIEvent *)event {
    CGPoint pt;
    float halfSide = 50.0f / 2.0f; //50.0f为UIButton的宽*高
    
    pt.x = (point.x - halfSide) / halfSide;
    pt.y = (point.y - halfSide) / halfSide;
    
    float xsquared = pt.x * pt.x;
    float ysquared = pt.y * pt.y;
    
    if((xsquared + ysquared) < 1.0) return YES;
    return NO;
}

- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {
    NSLog(@"++++ Valid Touch Events ++++");
}