方法时使用CoreText的CTRunDelegate

继 'unsafeBitCast' 撞车时使用CoreText方法时使用CoreText的CTRunDelegate

歇在最后一行'unsafeBitCast（...）'，

控制台登录代码“致命错误：'不能类型之间unsafeBitCast不同尺寸'

let str = " 2" 

    let mutableAttrStr = NSMutableAttributedString(string: str) 

     var callBack = CTRunDelegateCallbacks(version: kCTRunDelegateVersion1, dealloc: 

{ (obj) in 

    }, getAscent: { (obj) -> CGFloat in 
     return 40 
    }, getDescent: { (obj) -> CGFloat in 
     return 30 
    }) { (obj) -> CGFloat in 
     return 20 
    } 
    var imgUrl = "http://img3.3lian.com/2013/c2/64/d/65.jpg" 
    let callDelegate = CTRunDelegateCreate(&callBack,&imgUrl) 
    mutableAttrStr.addAttribute(kCTRunDelegateAttributeName as String, value: callDelegate!, range: NSRange.init(location: 0, length: 1)) 
     ... 
     ... 

     ... 
    let attributes = CTRunGetAttributes(run as! CTRun) as NSDictionary 

    let delegate = attributes.value(forKey: kCTRunDelegateAttributeName as String) 

    let imgPointer = CTRunDelegateGetRefCon(delegate as! CTRunDelegate) 

    let urlStr:String = unsafeBitCast(imgPointer, to: String.self);

imgPointer是实际UnsafeMutableRawPointer类型，但我必须把它转换成字符串告诉编译器

如果我这样做：

let imgPointer = CTRunDelegateGetRefCon(delegate as! CTRunDelegate) as! String

不幸的是，编译器警告：

任何帮助都很感激！

来源

2017-02-09 Oo_oO

'imgPointer'不是'String'，它是一个指向字符串的指针。你可以通过'let urlStr = imgPointer.load（as：String.self）来访问它指向的字符串' – dan

@dan你能告诉我'imgPointer.load（as：String.self）有什么区别吗？和'unsafeBitCast（imgPointer，to：String.self）'？ –

谢谢@dan，用方法'let urlStr = imgPointer.load(as: String.self)'替换'let urlStr:String = unsafeBitCast(imgPointer, to: String.self)'解决了这个问题。

来源

2017-02-11 18:31:43

方法时使用CoreText的CTRunDelegate

回答

相关问题