尝试调用类方法时出错:尝试索引本地“self"(一个 nil 值)-Lua [英] Error while trying to call a class method: attempt to index local 'self' (a nil value) - Lua

问题描述

我正在创建一个应该在 TI-Nspire 计算器上运行的 lua 脚本.问题是，在运行我的脚本时，当调用 button:activate() 方法时，我收到错误 Attempt to index local 'self' (a nil value).解析器说错误在下面代码的第 8 行.有问题的代码如下:

I'm creating a lua script that should run on the TI-Nspire calculator. The problem is that while running my script I get the error Attempt to index local 'self' (a nil value) when the button:activate() method is called. The parser says the error is in the 8th line in the code below. The problematic code is as follows:

button = class(view)

function button:init()
    self.selected = false
end

function button:activate()
    self.selected = true
end

我这样调用 activate 函数:

I call the activate function like this:

item = button()
local action = "activate"
local arguments = {}
item[action](unpack(arguments))

我知道stock"Lua 中不存在 class() 函数，它是 TI-Nspire Lua 实现中可用的函数.您可以在此处找到它的定义和用法.

I am aware the class() function doesn't exist in "stock" Lua, it's a function available in the TI-Nspire Lua implementation. You can find its definition and usage here.

推荐答案

obj:methodname(args) 是 obj.methodname(obj,args) 的糖.所以，如果你想使用语法item[action](unpack(arguments))，你需要使用item[action](item,unpack(arguments)).否则，如果可以显式使用方法，请尝试 item:activate(unpack(arguments)).

obj:methodname(args) is sugar for obj.methodname(obj,args). So, if you want to use the syntax item[action](unpack(arguments)), you need to use item[action](item,unpack(arguments)). Otherwise, try item:activate(unpack(arguments)) if you can use method explicitly.

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