小编rau*_*ora的帖子

在Xcode中重命名项目后出现此错误:

"error: linker command failed with exit code 1 (use -v to see invocation)" and 'Build failed'.

"ld: file not found:ld: file not found: /Users/admin/Library/Developer/Xcode/DerivedData/RenameProjectRenamed-glxemlqfmpgiasemfzifmxysyxpn/Build/Products/Debug-iphoneos/RenameProject.app/RenameProject"

你有什么想法吗？谢谢

如果传递了nil或者一些错误,Objective-C中的所有类的大多数都会返回nil,但NSURL会引发异常.具体来说,该方法[NSURL fileURLWithPath].

记录: "为此参数传递nil会产生异常."

但是,任何人都可以解释苹果会抛出异常而不是返回零吗？

我想用触摸事件来模拟橡皮擦效果,以显示顶部阻挡的图像,例如灰色;

像这样的东西:

我已经找到了很长时间的解决方案,但我做不好.

以下是我的自定义视图代码:CustomView.m:

-(id)initWithCoder:(NSCoder *)aDecoder
{
    if (self = [super initWithCoder:aDecoder]) {
        [self setup];
    }
    return self;
}

-(id)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self) {
        [self setup];
    }
    return self;

}
-(void)setup
{
    [self setMultipleTouchEnabled:NO];
    [self setBackgroundColor:[UIColor darkGrayColor]];
    self.drawingPath = [UIBezierPath bezierPath];
    [self.drawingPath moveToPoint:CGPointZero];
    [self.drawingPath setLineWidth:5.0];

    self.image = [UIImage imageNamed:@"transformers.jpg"];
    self.shapeLayer = [CAShapeLayer layer];
    self.caLayer = [CALayer layer];
    self.caLayer.frame = self.bounds;
    self.caLayer.contents = (id)(self.image.CGImage);
    [self.layer addSublayer:self.caLayer];
}
- (void)drawRect:(CGRect)rect
{
    self.shapeLayer.path = [self.drawingPath CGPath];

    self.caLayer.mask = self.shapeLayer; …