Returning a reference to a slice or retrning a slice of references

Hey,

So I have a function which should return a list of "Job" structs. What would be the prefered way to return it? Should it be a []Job or []Job ?

---

评论：

binaryblade:

Creating a pointer to a slice is silly. Just create a slice of however you want to naturally store your objects.

reus:

If they're read-only, use []Job, otherwise []*Job. 

zaib0n:

is the type of access should be the only concern ? 
passing the jobs by value means make a copy of each job, right ?
So wouldn't it be more efficient to pass jobs by reference, so the copy is not needed ?
I'm never sure what's the correct way to choose between the two

dshills:

That doesn't sound right. The slice will be copied but it carries a reference to the backing array. The reference will be copied but not the backing array. The jobs in the backing array would not get copied. The receiver would have a copied slice but full access to the original job backing array. Or am I missing something?

zaib0n:

you are right cause in this case we speak about a slice. But what if it was an array directly ?

dshills:

An interesting question actually. I think as soon as you try to pass it, it becomes a slice automagically. 

djherbis:

Arrays are copied when they are passed, they don't get converted to slices. If you want to convert an array to a slice just do: 

mySlice := myArray[:]

http://blog.golang.org/go-slices-usage-and-internals

dshills:

ahhhh that fills a knowledge hole. Thanks for the link.

mihai_stancu:

Slices themselves ar small enough to pass around by value and they were designed to be passed around by value. So a pointer to a slice wouldn't make that much sense.
If your Job objects are already in a slice by value ([]Job) then creating and passing a []Job slice would be trivial. While creating and passing a []*Job slice would require a few more lines of code.

DavidDavidsonsGhost:

Slices are references to arrays. They consist of a pointer to the backing array a capacity and a length. Just pass the slice around by value, unless you want to be able to modify the original slice.