Changing a complex table value through a reference

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#1

I am trying to change a complex table value through a reference. It’s probably easier to explain what I am trying to achieve with code.

Say we have the table:

local list = {
     ["Foo"] = {
          ["Bar"] = true
     }
}

We can change the value of Bar to false with a reference by doing:

list2 = list
list2["Foo"]["Bar"] = false
print(list["Foo"]["Bar"]) --The list's Bar value is now set to false!

I am trying to accomplish the same, but with a table that I can loop through to get to the value I want to change, like so:

local params = {"Foo", "Bar"}
list2 = list
for i = 1, #params do
     list2 = list2[params[i]]
end
list2 = false
print(list["Foo"]["Bar"]) --The list's Bar value is still true!

How can I accomplish the approach taken in example #2, but keeping the reference to the original list so it changes the original list’s “Bar” value to false?

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#2

Unfortunately you cannot do that since booleans aren’t objects in Lua, and plus you can’t bind a variable to a table field so that when the variable updates the key magically will as well. Just do list2.Foo.Bar = false

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#3

Hmm, is there any way I can make it to where I can specify a list of values to go through to get to a certain end point value and change that? I am looking for an efficient method where I can change any complex table value, because sometimes the table might not be as simple as the example one posted, and some values may be located in different locations.

I am trying to change any value in a given complex table all through one function based on the parameters given, is this possible?

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#4

Do you mean something like this?

find(t, key, value)

You could use some recursion to keep finding until you get the key you want and update it if you wish.

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#5

Just go up to #params - 1 and after the loop you can just do list2[params[#params]] = false

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#6

Wow! This actually worked when I tested it in the command prompt!
That’s a very interesting way to go about it… thank you!

1 Like