Re: Table in the generic for loop
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- Subject: Re: Table in the generic for loop
- From: Philipp Janda <siffiejoe@...>
- Date: 2016年3月20日 13:49:44 +0100
Am 20.03.2016 um 11:47 schröbte rst256:
Sample code:
rules=setmetatable({x=5,66,y=9}, { __call=pairs })
for k, v in rules do print(k, v) end
Output:
Infinite loop values k and v not changing, k == next and v==rules
Question:
This is normal, not bug?
Yes, this is normal.
Lua's for loop calls your table's `__call` metamethod (and as a result
`pairs(rules)`) on every iteration.
What should work is
rules = setmetatable( { x = 5, 66, y = 9 }, { __call = pairs } )
for k,v in rules() do print( k, v ) end
-- ^^
What you probably want is something like
rules = setmetatable( { x = 5, 66, y = 9 }, {
__call = function( st, _, var )
return next( st, var )
end
} )
for k,v in rules do print( k, v ) end
i.e. `rules` is called as an iterator, so it should behave like an
iterator. `pairs` on the other hand is an iterator *generator* (it
returns an iterator). You can't use `next` directly, because `__call`
adds another argument (the table), and your for-loop doesn't specify the
state variable that `next` expects (which would also be the table).
HTH,
Philipp