How to extend index from hooks?

Lua
1

Does any way exist to extend the index from appropriate hooks?

TL;DR

I am trying to extend index for pages with custom value. I dully hoped the following will work (intuitively):

```space-lua
event.listen {
  name = 'editor:pageSaved',
  run = function(e)
    e.testingVariable = e.lastModified
    print('Data', e.data)
    return e
  end
}
```

It seems the e is immutable or something because the print() call does not print the testingVariable at all.

2

You cannot extend page attributes, but you could create separate objects as part of the index process. The event to listen to is page:index.

You can then create new objects via the index.indexObjects API: API/index

3

OK, I will give it a try. But still, if the e in my example above is immutable, I should at least see some warning(s) in the console (which I don’t).

4

There isn’t really such a thing as immutable data in Lua

5

OOPS! My fault, there’s a typo in the code. :wink:

There isn’t really such a thing as immutable data in Lua

TL;DR

To explain more further… One can always play with table’s metamethods to gain poor man’s sort of “immutability” as some sort of “safety net” (if needed)…

function immutable(tbl)
  return setmetatable({}, {
    __index = tbl,
    __newindex = function(tbl, key, val)
      error('Cannot modify read-only table')
    end,
    __metatable = false
  })
end

local t = immutable { x = 1, y = 2, z = 3 } -- new "immutable" table `t`

It’s a nice trick but MUST NOT be considered as a “security feature” or something like that because the rawset() call can still be used to override this!

So, yes, there is simply no real immutability in Lua. :slight_smile: