blocks|key|3487991|text|尝尝这个|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3487992|if+(launchArgs+and+launchArgs.androidIntent+and+launchArgs.androidIntent.extras+
++++and+launchArgs.androidIntent.extras.notification+and+launchArgs.androidIntent.extras.notification.custom
++++and+launchArgs.androidIntent.extras.notification.custom.test_field)+then
--+do+you+stuff
end|code-block|syntax|javascript|3487993|此代码将检查每个表是否已设置。|3487994|如果您确定始终设置了启动args.androidIntent.extras，则只需执行以下操作|3487995|if(launchArgs.androidIntent.extras.notification+and+launchArgs.androidIntent.extras.notification.custom+and+launchArgs.androidIntent.extras.notification.custom.test_field)then
++++--+do+your+stuff
end|3487996|或只使用这个函数，这是我在其他一些答案中发布的(在这里也有帮助)|offset|length|style|BOLD|3487997|function+IndexScan(input,value,case,_type)
++++if+(input+and+type(input)+==+'table')+then
++++++++if+(_type)+then
++++++++++++if+(type(value)+==+_type+and+value+==+input)+then
++++++++++++++++return+true;
++++++++++++end
++++++++else
++++++++++++if+(type(value)+==+'table'+and+value+==+input)+then
++++++++++++++++return+true;
++++++++++++end
++++++++end
++++++++for+key,object+in+pairs(input)+do
++++++++++++if+(case+and+type(input)=='string'+and+type(key)=='string')+then
++++++++++++++++if+(_type)+then
++++++++++++++++++++if+(value:lower()+==+key:lower()+and+type(object)==_type)+then
++++++++++++++++++++++++return+true;
++++++++++++++++++++elseif(type(object)=='table')+then
++++++++++++++++++++++++return+IndexScan(object,value,case,_type)
++++++++++++++++++++end
++++++++++++++++else
++++++++++++++++++++if+(value:lower()+==+key:lower())+then
++++++++++++++++++++++++return+true;
++++++++++++++++++++elseif(type(object)=='table')+then
++++++++++++++++++++++++return+IndexScan(object,value,case,_type)
++++++++++++++++++++end
++++++++++++++++end
++++++++++++else
++++++++++++++++if+(_type)+then
++++++++++++++++++++if+(key+==+value+and+type(object)==_type)+then
++++++++++++++++++++++++return+true
++++++++++++++++++++elseif(type(object)=='table')+then
++++++++++++++++++++++++return+IndexScan(object,value,case,_type)
++++++++++++++++++++end
++++++++++++++++else
++++++++++++++++++++if+(key+==+value)+then
++++++++++++++++++++++++return+true
++++++++++++++++++++elseif(type(object)=='table')+then
++++++++++++++++++++++++return+IndexScan(object,value,case,_type)
++++++++++++++++++++end
++++++++++++++++end
++++++++++++end
++++++++end
++++end
++++return+false;
end
--+IndexScan(@param+table(table),+@param+index(string),+@param+case-sensitive(true/false),+@param+type+(index+type,+string/boolean/number/table+...))
--+checks+if+these+two+indexes+were+set+any+where+in+the+launchArgs+table+and+checks+their+type
if+(IndexScan(launchArgs,"notification",false,"table")+and+IndexScan(launchArgs,"test_field",false,"string"))+then
++++--+do+your+stuff
end|3487998|编辑：修复了函数中的一些错误。|3487999|编辑:在作者修复了通知错误之后，更新了脚本。|3488000|entityMap^0|0|0|0|0|0|0|W|0|0|0|3|0|0|G|0^^$0|@$1|2|3|4|5|6|7|10|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|11|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|12|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|13|8|@]|9|@]|A|$]]|$1|K|3|L|5|D|7|14|8|@]|9|@]|A|$E|F]]|$1|M|3|N|5|6|7|15|8|@$O|16|P|17|Q|R]]|9|@]|A|$]]|$1|S|3|T|5|D|7|18|8|@]|9|@]|A|$E|F]]|$1|U|3|V|5|6|7|19|8|@$O|1A|P|1B|Q|R]]|9|@]|A|$]]|$1|W|3|X|5|6|7|1C|8|@$O|1D|P|1E|Q|R]]|9|@]|A|$]]|$1|Y|3|-4|5|6|7|1F|8|@]|9|@]|A|$]]]|Z|$]]

Try this

<pre><code>if (launchArgs and launchArgs.androidIntent and launchArgs.androidIntent.extras 
 and launchArgs.androidIntent.extras.notification and launchArgs.androidIntent.extras.notification.custom
 and launchArgs.androidIntent.extras.notification.custom.test_field) then
-- do you stuff
end
</code></pre>

This code will check if each table is set.

If you're sure launch args.androidIntent.extras is always set you can just do this

<pre><code>if(launchArgs.androidIntent.extras.notification and launchArgs.androidIntent.extras.notification.custom and launchArgs.androidIntent.extras.notification.custom.test_field)then
 -- do your stuff
end
</code></pre>

OR Just use this function, that I posted in some other answer (helps here too )

<pre><code>function IndexScan(input,value,case,_type)
 if (input and type(input) == 'table') then
 if (_type) then
 if (type(value) == _type and value == input) then
 return true;
 end
 else
 if (type(value) == 'table' and value == input) then
 return true;
 end
 end
 for key,object in pairs(input) do
 if (case and type(input)=='string' and type(key)=='string') then
 if (_type) then
 if (value:lower() == key:lower() and type(object)==_type) then
 return true;
 elseif(type(object)=='table') then
 return IndexScan(object,value,case,_type)
 end
 else
 if (value:lower() == key:lower()) then
 return true;
 elseif(type(object)=='table') then
 return IndexScan(object,value,case,_type)
 end
 end
 else
 if (_type) then
 if (key == value and type(object)==_type) then
 return true
 elseif(type(object)=='table') then
 return IndexScan(object,value,case,_type)
 end
 else
 if (key == value) then
 return true
 elseif(type(object)=='table') then
 return IndexScan(object,value,case,_type)
 end
 end
 end
 end
 end
 return false;
end
-- IndexScan(@param table(table), @param index(string), @param case-sensitive(true/false), @param type (index type, string/boolean/number/table ...))
-- checks if these two indexes were set any where in the launchArgs table and checks their type
if (IndexScan(launchArgs,"notification",false,"table") and IndexScan(launchArgs,"test_field",false,"string")) then
 -- do your stuff
end
</code></pre>

EDIT:
Fixed some mistake in the function.

EDIT:
Updated the script after the author fixed the Notification typo.

blocks|key|3488019|text|也可以试试这个：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3488020|function+setglobal(name,value)
++++local+t=_ENV
++++local+f="_G"
++++for+x+in+name:gmatch("[%5E.]%2B")+do
++++++++if+t[f]==nil+then+t[f]={}+end
++++++++t=t[f]
++++++++f=x
++++end
++++t[f]=value
end

function+getglobal(name)
++++local+t=_ENV
++++for+x+in+name:gmatch("[%5E.]%2B")+do
++++++++t=t[x]
++++++++if+t==nil+then+return+nil,x+end
++++end
++++return+t
end

setglobal("launchArgs.androidIntent.extras.notification.custom.test_field",2014)
print(getglobal("launchArgs.androidIntent.extras.notification.custom.test_field"))
print(getglobal("launchArgs.androidIntent.extras.notifiaction.custom.test_field"))|code-block|syntax|javascript|3488021|这假设顶层变量是全局变量.根据需要进行调整。|3488022|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

Try also this:

<pre><code>function setglobal(name,value)
 local t=_ENV
 local f="_G"
 for x in name:gmatch("[^.]+") do
 if t[f]==nil then t[f]={} end
 t=t[f]
 f=x
 end
 t[f]=value
end

function getglobal(name)
 local t=_ENV
 for x in name:gmatch("[^.]+") do
 t=t[x]
 if t==nil then return nil,x end
 end
 return t
end

setglobal("launchArgs.androidIntent.extras.notification.custom.test_field",2014)
print(getglobal("launchArgs.androidIntent.extras.notification.custom.test_field"))
print(getglobal("launchArgs.androidIntent.extras.notifiaction.custom.test_field"))
</code></pre>

This assumes that the top-level variable is a global variable. Adapt as needed.

blocks|key|1885519|text|你可以用这个：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1885520|local+function+try(root,+query)
++local+ids,+len+=+{},+0
++for+id+in+query:gmatch("%25w%2B")+do
++++len+=+len+%2B+1
++++ids[len]=+id
++end

++local+node+=+root
++for+i=1,len+do
++++if+type(node)+~=+'table'+then+return+nil+end
++++node+=+node[ids[i]]
++end

++return+node
end|code-block|syntax|javascript|1885521|用法：|1885522|local+tbl+=+{+a+=+{+b+=+{+c+=+{+d+=+1+}+}+}+}

print(try(tbl,+'a.b.c.d'))+--+prints+1
print(try(tbl,+'a.b.c.x'))+--+prints+nil
print(try(tbl,+'a.x.c.d'))+--+prints+nil|1885523|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

You can use this:

<pre><code>local function try(root, query)
 local ids, len = {}, 0
 for id in query:gmatch("%w+") do
 len = len + 1
 ids[len]= id
 end

 local node = root
 for i=1,len do
 if type(node) ~= 'table' then return nil end
 node = node[ids[i]]
 end

 return node
end
</code></pre>

Usage:

<pre><code>local tbl = { a = { b = { c = { d = 1 } } } }

print(try(tbl, 'a.b.c.d')) -- prints 1
print(try(tbl, 'a.b.c.x')) -- prints nil
print(try(tbl, 'a.x.c.d')) -- prints nil
</code></pre>

I have problem; I must check in my program one field in table.

<pre><code>if(launchArgs.androidIntent.extras.notification.custom.test_field ~= nil)then...
</code></pre>

and when this index exist everything is ok, but when it isn't exist, I get an error :

<pre><code>Attempt to index field 'notification' (a nil value).
</code></pre>

And it is understandable. How check if that index exist?

Check if index in table exist

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我有问题，我必须在我的程序检查一个字段在表中。if(launchArgs.androidIntent.extras.notification.custom.test_field ~= nil)then...当这个索引存在时，一切都正常，但当它不存在时，我得到一个错误：Attempt to index field 'no...

问检查表中是否存在索引
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