表是Lua中唯一可帮助无涯教程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。Tables没有固定的大小,可以根据需要增加。
Tables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。
--sample table initialization mytable={} --simple table value assignment mytable[1]= "Lua" --removing reference mytable=nil -- lua garbage collection will take care of releasing memory
当有一个包含元素集的表table a 并将其分配给 b 时, a 和 b 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。
链接:https://www.learnfk.comhttps://www.learnfk.com/lua/lua-tables.html
来源:LearnFk无涯教程网
下面显示了一个示例,用于解释表的上述函数。
-- 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)
当无涯教程运行上面的程序时,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]]]) 根据给定的参数连接表中的字符串。 |
2 | table.insert(Table,[pos,] value) 在表中的指定位置插入一个值。 |
3 | table.maxn(table) 返回最大的数字索引。 |
4 | table.remove(table [,pos]) 从表中删除值。 |
5 | table.sort(table [,comp]) 根据可选的比较器参数对表进行排序。 |
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))
当无涯教程运行上面的程序时,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(insert)和删除(Remove)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])
当运行上面的程序时,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
经常需要按特定顺序对表格进行排序(Sorting Tables)。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
当无涯教程运行上面的程序时,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
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