我很无聊，看到这个问题（再次）和一个重复。
我开始写一些有趣的代码，结果是这样的：
local function getNeededVars(tab,func)
local needed,this = {}
this = setmetatable({},{
__index = function(s,k)
-- See if the requested variable exists.
-- If it doesn't, we obviously complain.
-- If it does, we log it and return the value.
local var = tab.vars[k]
if not var then
error("Eh, "..k.." isn't registered (yet?)",5)
end needed[k] = true return tab.vals[k]
end;
}) func(this) return needed
end
local function updateStuff(self,key,done)
for k,v in pairs(self.levars) do
if v.needed and v.needed[key] then
if not done[v] then done[v] = true
self.vals[v.name] = v.func(self)
updateStuff(self,v.name,done)
end
end
end
end
local function createSubTable(self,key,tab)
return setmetatable({},{
__newindex = function(s,k,v)
tab[k] = v updateStuff(self,key,{})
end; __index = tab;
})
end
local dependenceMeta
dependenceMeta = {
__index = function(self,k)
-- Allow methods, because OOP
local method = dependenceMeta[k]
if method then return method end
local variable = self.vars[k]
if not variable then
error("Variable "..k.." not found",2)
end return self.vals[k]
end;
__newindex = function(self,k,v)
local variable = self.vars[k]
if not variable then
error("Use :Register() to add stuff",2)
elseif type(v) == "table" then
self.vals[k] = createSubTable(self,k,v)
return updateStuff(self,k,{})
end self.vals[k] = v updateStuff(self,k,{})
end
}
function dependenceMeta:Register(var,value)
local varobject = {func=value,name=var}
self.vars[var] = varobject
table.insert(self.levars,varobject)
if type(value) == "function" then
varobject.needed = getNeededVars(self,value)
self.vals[var] = value(self)
elseif type(value) == "table" then
self.vals[var] = createSubTable(self,var,value)
elseif value then
self.vals[var] = value
end
end
function dependenceMeta:RegisterAll(tab)
for k,v in pairs(tab) do
self:Register(k,v)
end
end
local function DependenceTable()
return setmetatable({
levars = {};
vars = {};
vals = {};
},dependenceMeta)
end
local test = DependenceTable()
test:Register("border",{
x=20; y=50;
height=200;
width=100;
})
test:Register("body",function(self)
return {x=self.border.x+1,y=self.border.y+1,
height=self.border.height-2,
width=self.border.width-2}
end)
test:Register("font",function(self)
local size = (self.body.height+2)-(math.floor((self.body.height+2)/4)+1);
return { size = size; -- Since we use it in the table constructor...
height = size-4; --love.graphics.setNewFont( self.font.size ):getHeight();
-- I don't run this on love, so can't use the above line. Should work though.
}
end)
test:Register("padding",function(self)
local height = math.floor(self.border.height*(2/29))
return { height = height; width = height*3 } -- again dependency
end)
test:Register("text",{input=""}) -- Need this initially to keep input
test:Register("text",function(self)
return { input = self.text.input;
centerHeight = math.ceil(self.body.y+((self.body.height-self.font.height)/2));
left = self.body.x+self.padding.width+self.padding.height;
}
end)
test:Register("backspace",{key = false, rate = 3, time = 0, pausetime = 20, pause = true})
-- Again, didn't use gui.id() on the line below because my lack of LÖVE
test:Register("config",{active=true,devmode=false,debug=false,id=123,type='textbox'})
print("border.x=20, test.text.left="..test.text.left)
test.border = {x=30; y=50; height=200; width=100;}
print("border.x=30, test.text.left="..test.text.left)
test.border.x = 40
print("border.x=40, test.text.left="..test.text.left)
代码很多，但我喜欢写它。它给出了很好的输出：
border.x=20, test.text.left=73
border.x=30, test.text.left=83
border.x=40, test.text.left=93
只有在编辑其依赖项之一时才会重新计算所有属性。我让它也适用于子表，这有点棘手，但最后实际上看起来很容易。您可以编辑（例如） body 字段，方法是将其设置为全新的表或在现有表中设置字段，如最后几行所示的代码 sn-p。当您将其分配给新表时，它将在其上设置一个元表。您也不能使用对 (& co)，除非您使用 5.2 并且可以使用 __pairs。
它可能会解决您的问题。如果不是这样，我写它很开心，所以至少我写这篇文章总是积极的。 （你必须承认，那是一些漂亮的代码。嗯，它的工作方式，而不是实际的格式）
注意：如果您要使用它，请取消注释 love.graphics 和 gui.id 部分，因为我没有有 LÖVE，我显然必须测试代码。
这是我的东西 API 的快速“摘要”，因为它一开始可能会令人困惑：
local hmm = DependenceTable() -- Create a new one
print(hmm.field) -- Would error, "field" doesn't exist yet
-- Sets the property 'idk' to 123.
-- Everything except functions and tables are "primitive".
-- They're like constants, they never change unless you do it.
hmm:Register("idk",123)
-- If you want to actually set a regular table/function, you
-- can register a random value, then do hmm.idk = func/table
-- (the "constructor registering" only happens during :Register())
-- Sets the field to a constructor, which first gets validated.
-- During registering, the constructor is already called once.
-- Afterwards, it'll get called when it has to update.
-- (Whenever 'idk' changes, since 'field' depends on 'idk' here)
hmm:Register("field",function(self) return self.idk+1 end)
-- This errors because 'nonexistant' isn't reigstered yet
hmm:Register("error",function(self) return self.nonexistant end)
-- Basicly calls hmm:Register() twice with key/value as parameters
hmm:RegisterAll{
lower = function(self) return self.field - 5 end;
higher = function(self) return self.field + 5 end;
}
-- This sets the property 'idk' to 5.
-- Since 'field' depends on this property, it'll also update.
-- Since 'lower' and 'higher' depend on 'field', they too.
-- (It happens in order, so there should be no conflicts)
hmm.idk = 5
-- This prints 6 since 'idk' is 5 and 'field' is idk+1
print(hmm.field)
您可以使用 setfenv（如果是 Lua 5.1）来消除对“self.FIELD”的需求。借助一些环境魔法，您可以将“字段”的构造函数 （例如） 设为 function() return idk+1 end。