Lua Teal Interface Example

gistfile1.txt

local record IFoo
   bar: function(self:IFoo, integer):integer
end

--------------------

local record Foo1
   bar: function(integer):integer
end

function Foo1:bar(value:integer):integer
   return value + 1
end

function Foo1.new(): Foo1
   return setmetatable({ } as Foo1, { __index = Foo1 } as metatable<Foo1>)
end

--------------------

local record Foo2
   bar: function(integer):integer
end

function Foo2:bar(value:integer):integer
   return value - 1
end

function Foo2.new(): Foo2
   return setmetatable({ } as Foo2, { __index = Foo2 } as metatable<Foo2>)
end

--------------------

-- local foo_type = 1
local foo_type = 2

local function create_foo():IFoo
   if foo_type == 1 then
      return Foo1.new() as IFoo
   end

   return Foo2.new() as IFoo
end

local foo = create_foo()

print(foo:bar(2))