How to understand glVertexAttribPointer with UnsafeMutablePointer by Swift 4.2?

Question

I write some code about OpenGL ES. and I draw a triangle and want to put a image as texture on it. So I define a structure like this.

struct SceneVertor {
   var postion : GLKVector3
   var texture : GLKVector2

   init(_ value:(Float, Float, Float, Float, Float)) {
      self.postion = GLKVector3(v: (value.0, value.1, value.2))
      self.texture = GLKVector2(v: (value.3, value.4))
   }
}

but when I found glVertexAttribPointer function. Its last argument is the UnSafeRowPointer type . In Objective-C, this argument can be

Null + offsetof(SceneVertor, texture)

but I don't understand to change it by Swift .

In the Swift 4.2, we can calculate the offset like this

MemoryLayout<SceneVertor>.offset(of: \SceneVertor.texture)

now, how can I use it in the glVertexAttribPointer function.

thx.