In Objective-C these are two declarations of array of pointers:
NSArray<MTKMesh *> *mtkMeshes;
NSArray<MDLMesh *> *mdlMeshes;
I am struggling declaring the equivalent in Swift 3.0.
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1 Answer
MTKMesh and MDLMesh are classes (reference types). A variable
of type MTKMesh in Swift is a reference to an object instance,
i.e. what a variable of type MTKMesh * is in Objective-C.
Therefore you can simply declare
var mtkMeshes: [MTKMesh] = []
var mdlMeshes: [MDLMesh] = []
Each element of the array is a reference to an object instance:
let mesh1 = MDLMesh()
let mesh2 = MDLMesh()
mdlMeshes.append(mesh1)
mdlMeshes.append(mesh1)
mdlMeshes.append(mesh2)
print(mdlMeshes[0] === mdlMeshes[1]) // true
print(mdlMeshes[0] === mdlMeshes[2]) // false
The first two array elements reference the same object instance, the
last array element references a different instance.
(=== is the "identical-to" operator).
2 Comments
dugla
Thanks Martin. In your Swift equivalent I notice you have pre-allocated the arrays which is actually different then the Obj-C. For context, this is a snippet from code that uses mdlMeshes as an inout param to a function that allocates and populates that array. +1 for the '"===" tip.
Martin R
@dugla: You can also declare
var mtkMeshes: [MDLMesh]? and pass its address to a function func foo(meshes: inout [MDLMesh]?) which allocates and populates the array.