(Original) cocos2d-x 3.0 + Lua learning and work (4): common function (5): calculate the number of table elements: Table. Nums

The function here is mainly used to calculate the number of table elements. Reference: quick_cocos.

Xingyue's contribution ~~~

Let's look at a piece of code first.

local tbl = { [1] = 2, [2] = 2, [3] = 3 }print( "tbl length is " .. #tbl )

This code obtains the length of TBL, that is, the number of elements.

输出：tbl length is 3

There are three elements, no problem. We noticed that the subscript of the element is, that is, the key value is: 1, 2, 3. That is, TBL [1], TBL [2], and TBL [3]. If we modify the subscript, what will happen after the key is modified?

local tbl = { [1] = 2, [5] = 2, [3] = 3 }print( "tbl length is " .. #tbl )

输出：tbl length is 1

Can't you give me a few comments ~~~ (TOM: Why is it 1? Isn't it three elements ???)
The element length obtained by the # TBL method of table is only valid for the array and must start from 1 and be searched sequentially. Therefore, in the appeal, # TBL, search 1 is true, search 2. If no result is found, end the search. The returned result is 1.

Let's look at two examples:

local tbl = { [4] = 2, [5] = 2, [3] = 3 }print( "tbl length is " .. #tbl )输出：tbl length is 0

local tbl = { ["a"] = 2, ["b"] = 2, ["c"] = 3 }print( "tbl length is " .. #tbl )输出：tbl length is 0

 

Now go to the topic in this chapter to obtain the number of table elements. The Code is as follows:

--[[-- 计算表格包含的字段数量-- lua table 的 “#” 操作只对依次排序的数值下标数组有效，table.nums() 则计算 table中所有不为 nil 的值的个数。-- @param t 要检查的表格(t表示是table)-- @return integer 返回表格的字段数量--]]function table.nums( t )    local count = 0    local t = checkTable( t )    for k, v in pairs( t ) do        count = count + 1    end    return countend

Checktable is a function in my previous article. Link: http://www.cnblogs.com/wodehao0808/p/4015648.html.

The table. Nums method can be used to obtain the element. Attached example:

local tbl = { [4] = 2, [5] = 2, [3] = 3 }print( "tbl length is " .. table.nums( tbl ) )输出：tbl length is 3

This chapter ends now, Tom. Do you understand that there is no... (TOM: I have an IQ of 251, okay ....)
(Xingyue: Xiao Bai. You used to be 250 + 1)

(TOM :...)

 

The difference between the pairs and ipairs of the for loop is further illustrated at the end:

Pairs returns key and value. All elements in the table can be traversed. However, pairs traversal is random and unordered. (Xingyue: This feature has passed ...)

Ipairs traverses the array, similar to # TBL to obtain the number of elements. It also starts from 1 and is sequentially searched. For incremental search, ipairs is an ordered search.

 

This ends ~~~

 

The author uses cocos2d-x 3.0 + Lua learning and work experience, without the author's consent, please do not reprint! Thank you for your patience ~~~

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Address: http://www.cnblogs.com/wodehao0808/p/4021921.html

(Original) cocos2d-x 3.0 + Lua learning and work (4): common function (5): calculate the number of table elements: Table. Nums