[Swift] Required fields have default values in generated Swift code.

[Kenny Carruthers]

Given the following schema:

struct Position { 
  x: int64;
}

table Weapon { 
  strength: int64;
}

table Entity { 
  id: int64;
  position: Position (required);
  weapon: Weapon (required);
}

The Swift generated code uses force unwrapping for the required fields, but uses default values in initializers and constructors, effectively making the required fields optional.

public struct Entity: FlatBufferObject, Verifiable, ObjectAPIPacker {

  // snip... 

  // Optionals are force-unwrapped here.
  public var position: Position! { let o = _accessor.offset(VTOFFSET.position.v); return _accessor.readBuffer(of: Position.self, at: o) }
  public var weapon: Weapon! { let o = _accessor.offset(VTOFFSET.weapon.v); return Weapon(_accessor.bb, o: 

  // Note optional parameter for required field `position`.
  public static func add(position: Position?, _ fbb: inout FlatBufferBuilder) { ...}

  // Note non-optional parameter for required field `weapon`.
  public static func add(weapon: Offset, _ fbb: inout FlatBufferBuilder) { fbb.add(offset: weapon, at: VTOFFSET.weapon.p) }

  // Note optional parameter and default values for `position` and default value for `weaponOffset`.
  public static func createEntity(
    _ fbb: inout FlatBufferBuilder,
    id: Int64 = 0,
    position: Position? = nil,
    weaponOffset weapon: Offset = Offset()
  ) -> Offset {
    let __start = Entity.startEntity(&fbb)
    Entity.add(id: id, &fbb)
    Entity.add(position: position, &fbb)
    Entity.add(weapon: weapon, &fbb)
    return Entity.endEntity(&fbb, start: __start)
  }

  // snip ...
}

Is this the intended behaviour? At least in the Swift implementation, the current behaviour allows the caller to create a new FlatBuffer without specifying a value for a required field.

(Or is "nil" considered a valid value for a required field within the world of FlatBuffers?)

[mustiikhalil]

Hey, thanks for opening the issue!

Looks like a bug to me (at least in the createEntity function. since that should not allow the user to create default fields if they are required.

[mustiikhalil]

@kennycarruthers Regarding this issue after looking into it a bit

We do verify if the fields are added when we run endMonster which runs fbb.require(table: end, fields: [10]); and thus we don't really need to make the functions require the value. However, it seems that the proper approach would be fixing it