Metatables, getting the name of the value you set.

[rokit boy]

So I have been working with OOP using metatables and I scribbled out this:

Code: Select all

Letters = {}

newLetter = {}

setmetatable(newLetter,{ __call = function(table,character,upper)
    local letter = {actualChar = character, uppercase = upper}
    return letter
})

So the syntax is very oop like.
I came across one obstacle.
I want to add it to the Letters table, but for the same name I gave it.
So if I have:

Code: Select all

A = Letter("A",true)

How can I make it so it will be accessible through the Letters table like this:

Code: Select all

Letters.A

[Xgoff]

So I have been working with OOP using metatables and I scribbled out this:

Code: Select all

Letters = {}

newLetter = {}

setmetatable(newLetter,{ __call = function(table,character,upper)
    local letter = {actualChar = character, uppercase = upper}
    return letter
})

So the syntax is very oop like.
I came across one obstacle.
I want to add it to the Letters table, but for the same name I gave it.
So if I have:

Code: Select all

A = Letter("A",true)

How can I make it so it will be accessible through the Letters table like this:

Code: Select all

Letters.A

Code: Select all

Letters = {}

newLetter = {}

setmetatable(newLetter,{ __call = function(table,character,upper)
    local letter = {actualChar = character, uppercase = upper}
    Letters[character] = letter
    return letter
end
})

[rokit boy]

...

Did you listen to me?

What if I do:

Code: Select all

Asterisk = Letter("*",false)

and I want it to be:

Code: Select all

Letters.Asterisk

[Xgoff]

...

Did you listen to me?

What if I do:

Code: Select all

Asterisk = Letter("*",false)

and I want it to be:

Code: Select all

Letters.Asterisk

if you want to do this then you need to have __newindex set on the environment (you will really want a separate env for this). the Letter function is going to need some way of indicating that the table it returns is special, so that the environment's __newindex can handle them specially

as an example, but using the global environment: http://codepad.org/Micbz3xO

btw, this won't work if you're assigning to locals

[Inny]

You can place a metatable on Letters and change the syntax slightly

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Letters = setmetatable({}, {
  __index = function(T, k, v)
    return function( something, whatever )
      rawset(T, k, { something, whatever } ) -- your code here
      return rawget( T, k )
  end
})

Letters.Asterisk( "*", true )
print( Letters.Asterisk )

local grave = Letters.Grave( "`", false )
print( grave, Letters.Grave )

[trubblegum]

Assigning globals in a constructor is bad.

Code: Select all

letters = {}

letter = {}
letter.new = function(this, character) return setmetatable({character = character}, {__index = this}) end -- presumably
setmetatable(letter, {__call = letter.new})

letters.asterisk = letter('*')

[rokit boy]

Thanks people!