deep copying / .dup / template object.dup cannot deduce function from argument types

Alex Parrill via Digitalmars-d-learn digitalmars-d-learn at puremagic.com
Sun Dec 13 13:35:56 PST 2015


On Sunday, 13 December 2015 at 18:54:24 UTC, Robert M. M√ľnch 
wrote:
> Hi, I just wanted to naively copy an object and used:
>
> a = myobj.dup;
>
> and get the following error messages:
>
> source/app.d(191): Error: template object.dup cannot deduce 
> function from argument types !()(BlockV), candidates are:
> /Library/D/dmd/src/druntime/import/object.d(1872):        
> object.dup(T : V[K], K, V)(T aa)
> /Library/D/dmd/src/druntime/import/object.d(1908):        
> object.dup(T : V[K], K, V)(T* aa)
> /Library/D/dmd/src/druntime/import/object.d(3246):        
> object.dup(T)(T[] a) if (!is(const(T) : T))
> /Library/D/dmd/src/druntime/import/object.d(3262):        
> object.dup(T)(const(T)[] a) if (is(const(T) : T))
> /Library/D/dmd/src/druntime/import/object.d(3273):        
> object.dup(T : void)(const(T)[] a)
>
> Hmm... so, is .dup not the way to go?
>
> And, am I correct, that a deep-copy needs to be hand coded?

`dup` is an array method; it only works on arrays.

Structs are value types, so `a = b` will "duplicate" a struct. 
For classes, you will need to define your own clone function.


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