Re: Logging changes of a weak table

[Zhao Han <hz@...>]

Thanks. That’s what I needed. 

With a little improvement:

—

sentry[r] = setmetatable({val = r}, { __gc = function(o) print(o.val, 'is gc-ed') end})

—

Best Regards,

/hz 

在 2018年9月4日，上午2:55，云风 Cloud Wu <cloudwu@gmail.com> 写道：

Zhao Han <hz@fiosoftware.com>于2018年9月4日周二 上午12:01写道：

What if the value is not a table? 

---

tab = {}

setmetatable(tab, {__mode = 'v'})

r = function() end

tab['key'] = r

r = nil

collectgarbage()

—

When ‘r' is collected, how could ‘tab’ know that?

Thanks.

/hz

You can use a sentry table like this :

sentry = setmetatable({}, { __mode = "kv" })

sentry[r] = setmetatable({}, { __gc = function() print "r is collected" end })

btw, Pay attention about weak keys, they would removed from weak table AFTER running their finalizers.