就像标题一样，我有一些Objective-c代码，我如何在Swift3中使用它们CGContextSaveGState(context);CGContextSetTextMatrix(context,CGAffineTransformIdentity);CGContextTranslateCTM(context,0,size.height);CGContextScaleCTM(context,1.0,-1.0);CGMutablePathRefpath=CGPathCreateMutable();CGPathAddRect(path,NULL,CGRectMake(0,0,size.w