如何获取CGPDFDictionaryRef键 [英] How to get CGPDFDictionaryRef keys

问题描述

我想得到一个CGPDFDictionaryRef的所有键。到目前为止，我发现从stackoverflow

这里我的代码是swift：

  func printPDFKeys（key：UnsafePointer< Int8>，ob：CGPDFObjectRef，info：UnsafeMutablePointer& >） - > Void {
 
 NSLog（key =％s，key）; 
 // return（key，ob，info）
} 
  

然后被称为这样。

  let myDoc = CGPDFDocumentCreateWithURL（url）
 if myDoc！= nil {
 let myCatalog = CGPDFDocumentGetCatalog myDoc）
 
 CGPDFDictionaryApplyFunction（myCatalog，printPDFKeys，nil）; //这里的编译器错误
} 
  

但是我收到一个错误，

ac函数指针只能从引用 func'
或文字关闭

我也尝试过使用这样的Closure：

  var printPDFKeys：（UnsafePointer< Int8>，CGPDFObjectRef，UnsafeMutablePointer（）） - > Void 
 
 printPDFKeys = {
 key，ob，info in 
 
 NSLog（key =％s，key）; 
 
} 
  

我仍然收到同样的错误。我该怎么办？

解决方案

正确的关闭语法将是：

  CGPDFDictionaryApplyFunction（myCatalog，{（key，object，info） - > Void in 
 // do something 
}，nil）
  

I would like to get all the keys of an CGPDFDictionaryRef. so far this what I found from stackoverflow

Here is my code in swift:

 func printPDFKeys(key: UnsafePointer<Int8>, ob: CGPDFObjectRef, info: UnsafeMutablePointer<()>) -> Void{

 NSLog("key = %s", key);
   //return (key, ob , info)
  }

This function is then called like this.

     let myDoc = CGPDFDocumentCreateWithURL(url)
    if myDoc != nil {
    let myCatalog=CGPDFDocumentGetCatalog(myDoc)

       CGPDFDictionaryApplyFunction(myCatalog, printPDFKeys, nil);//Compiler error here
     }

However I am getting an error that

a c function pointer can only be formed from a reference to a 'func' or a literal closure

I have also tried using a Closure like this:

var printPDFKeys: (  UnsafePointer<Int8>, CGPDFObjectRef,  UnsafeMutablePointer<()> )-> Void

    printPDFKeys={
        key,ob,info in

    NSLog("key = %s", key);

    }

I am still getting the same error. How could I go about it

解决方案

the correct closure syntax would be:

CGPDFDictionaryApplyFunction(myCatalog, { (key, object, info) -> Void in
// do something
}, nil)

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