Re: AW: Size of a non numerical indexed table
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- Subject: Re: AW: Size of a non numerical indexed table
- From: Rici Lake <lua@...>
- Date: 2005年8月31日 17:21:16 -0500
On 31-Aug-05, at 4:42 PM, Romulo Bahiense wrote:
i haven't used metatables so far but the basics are to check, on
assignment,
wether the index is a string and wether the value is nil (delete
index) or
not (new index) and based on that, update a counter in the table
Lua 5.0.2 don't call __newindex when the value is nil (don't ask me
why).
In your example, it doesn't call it because the index isn't 'new'
> t = setmetatable({}, {__newindex=function(self,k,v) print(k,v)
rawset(self,k,v) end})
> t.a = nil
a nil
> t.a = nil
a nil
> t.a = 5
a 5
> t.a = nil
> t.a = 5
a 5
> t.a = 6
__newindex is called if the lookup of the key returns nil (i.e. the key
wasn't found.) Setting a key to nil effectively deletes it from the
table, so the next set will be "new" again.