Hello everyone,
Currently Swift only supports computed properties for each enum case.
If you want to somehow get static values with each case you would
probably do it like this:
enum Planet {
case mercury
case venus
case earth
case mars
case jupiter
case saturn
case uranus
case neptune
var mass: Float {
switch self {
case .mercury: return 3.303e+23
case .venus: return 4.869e+24
case .earth: return 5.976e+24
case .mars: return 6.421e+23
case .jupiter: return 1.9e+27
case .saturn: return 5.688e+26
case .uranus: return 8.686e+25
case .neptune: return 1.024e+26
}
}
var radius: Float {
switch self {
case .mercury: return 2.4397e6
case .venus: return 6.0518e6
case .earth: return 6.37814e6
case .mars: return 3.3972e6
case .jupiter: return 7.1492e7
case .saturn: return 6.0268e7
case .uranus: return 2.5559e7
case .neptune: return 2.4746e7
}
}
}
However I see two problems with this approach:
1. These value definitions are spread out and difficult to read and
maintain (especially if you have many computed properties for each
enum case);
2. These values are not static. They are computed each time property
is accessed. This can be a problem when value is expensive to create.
The proposed solution is to have single static initializer for each
enum case that initializes stored properties. For example,
enum Planet {
var mass: Float
var radius: Float
static init(mass: Float, radius: Float) {
self.mass = mass
self.radius = radius
}
case mercury where (mass: 3.303e+23, radius: 2.4397e6)
case venus where (mass: 4.869e+24, radius: 6.0518e6)
case earth where (mass: 5.976e+24, radius: 6.37814e6)
case mars where (mass: 6.421e+23, radius: 3.3972e6)
case jupiter where (mass: 1.9e+27, radius: 7.1492e7)
case saturn where (mass: 5.688e+26, radius: 6.0268e7)
case uranus where (mass: 8.686e+25, radius: 2.5559e7)
case neptune where (mass: 1.024e+26, radius: 2.4746e7)
}
This approach do not affect enums that have raw or associated values,
or custom enum initializers:
case A = "A" where (id: 0)
or
case B(Int, Int, Int) where (id: 0)
Benefits:
1. Less verbosity
2. Improved readability
3. Related values are closer to each other
4. Static values are not recomputed
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