• David Zhang (14/14) Sep 17 2017 Hi,
• David Zhang (3/17) Sep 17 2017 I am aware that you can duplicate the method, but it seems a bit
• David Zhang (3/3) Sep 17 2017 Nevermind! I rediscovered the `inout`attribute.
• Steven Schveighoffer (6/11) Sep 17 2017 Correct, inout applied to the function is actually applying to the

David Zhang <straivers98 gmail.com> writes:

Hi,

I have a class `Image`, and I have a function called 
`getSubImage(Rect bounds)`. What I can't figure out is how to get 
the result of `getSubImage()` to take on the constness of the 
backing image.

ie.
     //The Image class is really just a view over a buffer that's 
managed elsewhere
     const(Image).getSubImage(...) -> const(Image)

     Image.getSubImage(...) -> Image

I tried to do this with `inout`, but that requires that a 
parameter in the function be `inout`. I don't suppose I could 
somehow declare `this` to be inout?

Thanks

David Zhang <straivers98 gmail.com> writes:

On Sunday, 17 September 2017 at 21:18:08 UTC, David  Zhang wrote:
 Hi,

 I have a class `Image`, and I have a function called 
 `getSubImage(Rect bounds)`. What I can't figure out is how to 
 get the result of `getSubImage()` to take on the constness of 
 the backing image.

 ie.
     //The Image class is really just a view over a buffer 
 that's managed elsewhere
     const(Image).getSubImage(...) -> const(Image)

     Image.getSubImage(...) -> Image

 I tried to do this with `inout`, but that requires that a 
 parameter in the function be `inout`. I don't suppose I could 
 somehow declare `this` to be inout?

 Thanks

I am aware that you can duplicate the method, but it seems a bit 
unwieldy and excessive.

David Zhang <straivers98 gmail.com> writes:

Nevermind! I rediscovered the `inout`attribute.

Though if I may say so, I have no idea how `inout` is supposed to 
indicate "whatever the constness of a".

Steven Schveighoffer <schveiguy yahoo.com> writes:

On 9/17/17 5:37 PM, David Zhang wrote:
 Nevermind! I rediscovered the `inout`attribute.

Correct, inout applied to the function is actually applying to the 
'this' parameter. Same as const or immutable functions as well.

 
 Though if I may say so, I have no idea how `inout` is supposed to 
 indicate "whatever the constness of a".
 

What inout does is look at the mutability of the parameter and transfer 
it to the mutability of the return type.

-Steve