c++ - handle single-dimensional array in Microsoft Interface Definition Language

Question

I followed the instruction at

https://learn.microsoft.com/en-us/uwp/midl-3/intro

try to use single-dimensional array in c++ winRT component

Class.idl

namespace MyClass  
{  
    [default_interface]  
    runtimeclass Class  
    {  
        Class();  
        String[] aaa(String[] v);  
      
    }  
}  

Class.h

#pragma once  
  
#include "Class.g.h"  
  
namespace winrt::MyClass::implementation  
{  
    struct Class : ClassT<Class>  
    {  
        Class() = default;  
  
        hstring[] aaa(hstring[]  s);  
   
    };  
}  
namespace winrt::MyClass::factory_implementation  
{  
    struct Class : ClassT<Class, implementation::Class>  
    {  
    };  
}  

Class.cpp

#include "pch.h"  
#include "Class.h"  
#include "Class.g.cpp"  
  
namespace winrt::MyClass::implementation  
{  
  
  hstring[] Class::aaa(hstring[] s)  
    {  
        return null;  
    }  
   
  
}  

but it reports the error as below

it looks like 'hstring[]' is not correct

Is there any sample code for usage of a single-dimensional array?

thanks

Answer 1

Hello,

Welcome to Microsoft Q&A!

We usually use com_array<hstring> to pass parameters to and from Windows Runtime APIs instead of hstring[] when a String[] declared in an idl file. In addition, you do not need to manually write the prototype of the aaa method. The midl.exe > cppwinrt.exe tool chain will implement templates including the definition and declaration of aaa method in Generated Files(\Project-Name\RuntimeComponent\Generated Files\sources). For more information, you can refer to this document. You could also check the following steps:

First: Declare the String[] aaa(String[] v); in Class.idl of the component.

namespace RuntimeComponent  
{  
    [default_interface]  
    runtimeclass Class  
    {  
        Class();  
        Int32 MyProperty;  
  
        String[] aaa(String[] v);  
    }  
}  

Second: Save and build the project.

Third: Open the folder \Project-Name\RuntimeComponent\Generated Files\sources in your project folder, open the Class.h and Class.cpp files and copy the definition and declaration code of aaa into the component.

Class.h

namespace winrt::RuntimeComponent::implementation  
{  
    struct Class : ClassT<Class>  
    {  
        ……  
  
        com_array<hstring> aaa(array_view<hstring const> v);  
    };  
}  

Class.cpp

namespace winrt::RuntimeComponent::implementation  
{  
    ……  
    com_array<hstring> Class::aaa(array_view<hstring const> v)  
    {  
        throw hresult_not_implemented();  
    }  
}  

For more information about winrt::com_array struct template, you can refer to the document.