Re: Multiple alias this is coming.

[IgorStepanov via Digitalmars-d-announce]

On Thursday, 18 September 2014 at 22:16:23 UTC, bearophile wrote:

IgorStepanov:

Do you ask about alias this or about it multiple usage. Multiple usage is similar to single, but multiple:)

I meant the multiple usage. And none of your examples here are use cases :-( I'd like to see one use case, or more.

Bye,
bearophile

For example, you can define struct (value-type with automatic
storage class) which implements interfaces:

intarface InputStream
{
    ...
}

intarface OutputStream
{
    ...
}
struct File
{
    this(string name, string options)
    {
        impl = new FileImpl(name, options);
    }

    ~this()
    {
        impl.close();
    }

    @property InputStream inputStream()
    {
       return new class(impl) InputStream
       {
           //InputStream implementation
           ...
       }
    }

    @property OutputStream outputStream()
    {
       return new class(impl) OutputStream
       {
           //OutputStream implementation
           ...
       }
    }

    alias inputStream this;
    alias seekable this;
    FileImpl* impl;
}


Record[] readData(InputStream);
void storeData(OutputStream, Record[]);

Record[] extractRecords()
{
    File f = File("records.bin", "rw");
    auto data = readData(f);
    ///split to extracted and remaining
    f.truncate();
    writeData(f, remaining);
    return extracted;
}