Is it possible for a table, when referenced without a key, to return a particular value rather than a reference to itself?
Let's say I have the following table:
local person = {
name = "Kapulani",
level = 100,
age = 30,
}
In Lua, I can quite easily refer to "person.name", "person.level", or "person.age" and get the values as expected. However, I have certain cases where I may want to just reference "person" and, instead of getting "table: " I'd like to return the value of "person.name" instead.
In other words, I'd like person.x (or person[x]) to return the appropriate entry from the table, but person without a key to return the value of person.name (or person["name"]). Is there a mechanism for this that I haven't been able to find?
I have had no success with metatables, since __index will only apply to cases where the key does not exist. If I put "person" into a separate table, I can come up with:
local true_person = {
... -- as above
}
local env_mt = {
__index = function(t, k)
if k == 'person' then
return true_person
end
end
}
local env = setmetatable( {}, env_mt )
This lets me use __index to do some special handling, except there's no discernable way for me to tell, from __index(), whether I'm getting a request for env.person (where I'd want to return true_person.name) or env.person[key] (where I'd want to return true_person as a table, so that 'key' can be accessed appropriately).
Any thoughts? I can approach this differently, but hoping I can approach this along these lines.
You can do it when the table is being used as a string by setting the __tostring
metatable entry:
$ cat st.lua
local person = {
name = "Kapulani",
level = 100,
age = 30,
}
print(person)
print(person.name)
print(person.age)
setmetatable(person, {__tostring = function(t) return t.name end})
print(person)
$ lua st.lua
lua st.lua
table: 0x1e8478e0
Kapulani
30
Kapulani