Where to store constant values in swift?

Question

I'm trying to build my first spritekit game in swift. I don't understand where to store constants so I can make them available to the whole project. I have some experience with C++ and I used to create a Constants.h file. Is there such thing in Swift? What's the recommended practice to do this?

Right now I'm using a struct with static constants but I'm not sure if it's the right way to do it:

struct Constants {
    static let gravity : Int = 20
}

Answer 1

struct Constants {
    static let buildName = "Orange-Pie"

    struct FacebookConstants {
     static let clientId ="asdasdsa"
   }
    struct TwitterConstants {
     static let clientId ="asdasdsa"
   }
}

Use :

Constants.FacebookConstants.clientId

Answer 2

If you have highly generic constants needed by every part of your program, this is indicating a design problem (whenever you are at a loss of where something should go, you probably have a design problem). Things like a gravitational constant shouldn't be necessary for the vast majority of the program, so they generally don't need to be global constants (that's true in C++, too).

Put your constants with the thing that needs that constant, or pass them into the thing that needs that constant. SpriteKit should do most gravity calculations for you, but if you're doing additional physics work, then there should be some object that represents the physics engine or "the world." That's where the gravity constant belongs. Alternately, put the gravity constant into a struct that you pass into the physics engine at launch.

Even if you do have very broad need of the gravitational constant, then you should put it into a struct like PhysicalConstants, not a generic Constants (which makes code reuse hard because it mixes unrelated things). A common case of this in my code are "style" constants like "the systemwide highlight color" (which are likely to be changed by the client, so I want a single place to modify them). These go into a header called Style.h in my apps, and now would go into a Style struct. But they're kept separate from non-style constants.