详解Lua中的表的概念及其相关操作方法
时间：2021-04-27 09:08:06 | 栏目：Ruby | 点击：次
表格是唯一的数据结构中Lua可以帮助我们创造出不同的类型，如数组和字典。 Lua使用关联数组和可不仅数字，但也有不同的零字符串索引。表格都没有固定的大小，并根据需要可以增长。
Lua采用的所有陈述，包括包装的代表性表。当我们访问一个方法的字符串。格式，这意味着，我们正在访问的格式化功能的字符串封装。
表示和用法
表称为对象和它们既不值，也没有变。 Lua使用构造函数表达式{}创建一个空表。它是要知道，有保存表的参考和表本身的变量之间没有固定的关系。
复制代码 代码如下:
--sample table initialization
mytable = {}
mytable = {}
--simple table value assignment
mytable[1]= "Lua"
--removing reference
mytable = nil
-- lua garbage collection will take care of releasing memory
当我们有一个表与集合的元素，如果我们将其指定为b，a和b都指向相同的内存。没有单独的内存单独分配对b。当设置为无，表将仍然可以访问到b。当没有引用表，然后在Lua垃圾收集需要清理过程，使这些未引用的内存再次被重用。
一个例子如下所示用于说明表的上述特征。
复制代码 代码如下:
-- Simple empty table
mytable = {}
print("Type of mytable is ",type(mytable))
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("mytable 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，会得到下面的输出
复制代码 代码如下:
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
mytable 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
mytable Element at index 1 is Lua
mytable Element at index wow is Tutorial
alternatetable Element at index 1 is Lua
mytable 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
表操作
在对表操作内置函数和它们被列于下表中。
让我们看看上面的函数一些例子。
表串联
我们可以使用concat函数来连接，如下所示的两个表。
复制代码 代码如下:
fruits = {"banana","orange","apple"}
-- returns concatenated string of table
print("Concatenated string ",table.concat(fruits))
-- 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，会得到下面的输出
复制代码 代码如下:
Concatenated string bananaorangeapple
Concatenated string banana, orange, apple
Concatenated string orange, apple
Concatenated string banana, orange, apple
Concatenated string orange, apple
插入和删除
插入在表中的项目，并除去最常见于表操纵。它下面的解释。
复制代码 代码如下:
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，会得到下面的输出
复制代码 代码如下:
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
Fruit at index 2 is grapes
The maximum elements in table is 5
The last element is mango
The previous last element is nil
排序表格
排序表通常需要和排序函数表中的元素按字母顺序排序。下图所示为这方面的一个范例。
复制代码 代码如下:
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
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，会得到下面的输出
复制代码 代码如下:
1 banana
2 orange
3 apple
4 grapes
sorted table
1 apple
2 banana
3 grapes
4 orange
2 orange
3 apple
4 grapes
sorted table
1 apple
2 banana
3 grapes
4 orange