📅 最后修改于: 2020-10-16 05:13:30 🧑 作者: Mango
表是Lua中唯一可帮助我们创建数组和字典等不同类型的数据结构。 Lua使用关联数组，不仅可以用数字索引，还可以用字符串（除nil外）进行索引。桌子没有固定的大小，可以根据我们的需要增加。
Lua在所有表示形式（包括程序包表示形式）中使用表。当我们访问方法字符串.format时，这意味着我们正在访问字符串包中可用的格式函数。
表称为对象，它们既不是值也不是变量。 Lua使用构造函数表达式{}创建一个空表。众所周知，持有表引用的变量与表本身之间没有固定的关系。
--sample table initialization
mytable = {}
--simple table value assignment
mytable[1]= "Lua"
--removing reference
mytable = nil
-- lua garbage collection will take care of releasing memory
当我们拥有一个包含元素集的表a并将表赋给b时， a和b都引用相同的内存。没有为b单独分配单独的内存。当a设置为nil时，b仍然可以访问表。当没有对表的引用时，Lua中的垃圾回收将负责清理过程，以使这些未引用的内存可以再次使用。
下面显示了一个示例，用于解释表的上述功能。
-- Simple empty table
mytable = {}
print("Type of mytable is ",type(mytable))
mytable[1]= "Lua"
mytable["wow"] = "Tutorial"
print("mytable Element at index 1 is ", mytable[1])
print("mytable Element at index wow is ", mytable["wow"])
-- alternatetable and mytable refers to same table
alternatetable = mytable
print("alternatetable Element at index 1 is ", alternatetable[1])
print("alternatetable Element at index wow is ", alternatetable["wow"])
alternatetable["wow"] = "I changed it"
print("mytable Element at index wow is ", mytable["wow"])
-- only variable released and and not table
alternatetable = nil
print("alternatetable is ", alternatetable)
-- mytable is still accessible
print("mytable Element at index wow is ", mytable["wow"])
mytable = nil
print("mytable is ", mytable)
当我们运行上面的程序时，我们将获得以下输出-
Type of mytable is table
mytable Element at index 1 is Lua
mytable Element at index wow is Tutorial
alternatetable Element at index 1 is Lua
alternatetable Element at index wow is Tutorial
mytable Element at index wow is I changed it
alternatetable is nil
mytable Element at index wow is I changed it
mytable is nil
内置了用于表操作的函数，这些函数在下表中列出。
| Sr.No. | Method & Purpose |
|---|---|
| 1 |
table.concat (table [, sep [, i [, j]]]) Concatenates the strings in the tables based on the parameters given. See example for detail. |
| 2 |
table.insert (table, [pos,] value) Inserts a value into the table at specified position. |
| 3 |
table.maxn (table) Returns the largest numeric index. |
| 4 |
table.remove (table [, pos]) Removes the value from the table. |
| 5 |
table.sort (table [, comp]) Sorts the table based on optional comparator argument. |
让我们看看上述功能的一些示例。
我们可以使用concat函数来连接两个表，如下所示-
fruits = {"banana","orange","apple"}
-- returns concatenated string of table
print("Concatenated string ",table.concat(fruits))
--concatenate with a character
print("Concatenated string ",table.concat(fruits,", "))
--concatenate fruits based on index
print("Concatenated string ",table.concat(fruits,", ", 2,3))
当我们运行上面的程序时，我们将获得以下输出-
Concatenated string bananaorangeapple
Concatenated string banana, orange, apple
Concatenated string orange, apple
在表操作中，表项的插入和删除是最常见的。下面说明。
fruits = {"banana","orange","apple"}
-- insert a fruit at the end
table.insert(fruits,"mango")
print("Fruit at index 4 is ",fruits[4])
--insert fruit at index 2
table.insert(fruits,2,"grapes")
print("Fruit at index 2 is ",fruits[2])
print("The maximum elements in table is",table.maxn(fruits))
print("The last element is",fruits[5])
table.remove(fruits)
print("The previous last element is",fruits[5])
当我们运行上面的程序时，我们将获得以下输出-
Fruit at index 4 is mango
Fruit at index 2 is grapes
The maximum elements in table is 5
The last element is mango
The previous last element is nil
我们经常需要按特定顺序对表格进行排序。排序功能按字母顺序对表中的元素进行排序。如下所示。
fruits = {"banana","orange","apple","grapes"}
for k,v in ipairs(fruits) do
print(k,v)
end
table.sort(fruits)
print("sorted table")
for k,v in ipairs(fruits) do
print(k,v)
end
当我们运行上面的程序时，我们将获得以下输出-
1 banana
2 orange
3 apple
4 grapes
sorted table
1 apple
2 banana
3 grapes
4 orange