LUA和电晕错误:尝试调用方法''(一个Nil值)-使我疯狂 [英] LUA and Corona error: Attempt To Call Method ' ' (A Nil Value) - Driving Me Crazy
问题描述
我会问你一个错误,这使我发疯.
I would ask your help for an error that is driving me crazy.
哦...我正在将LUA与Corona SDK结合使用...
Ohh... I'm using LUA with Corona SDK btw...
我正在创建船的实例.正在实例化飞船,我可以访问其属性,但不能访问任何方法!遵循代码,我不知道该怎么办:
I am creating an instance of a ship. The ship is being instantiated, I can access its properties, but I can not access any method!! Follow the codes, I do not know what to do:
spaceShip.lua:
spaceShip.lua:
require('gameConf')
spaceShip = {}
spaceShip.__index = spaceShip
function spaceShip:New(posX, posY, width, height)
local _spaceShip = nil
_spaceShip = {}
setmetatable(_spaceShip, spaceShip)
_spaceShip = display.newRect(posX - width/2, posY - height/2, width, height)
_spaceShip:setFillColor(140, 140, 140, 0)
_spaceShip.width = width
_spaceShip.height = height
local shipShape = { -width/2, -height/2, width/2, -height/2, width/2, height/2, -width/2, height/2 }
local shipShapeMaterial = { density = 1.0, friction = 1.0, bounce = 0.0 , shape = shipShape}
local shipMotor = { -width/2, height/3, width/2, height/3, width/2, height/2, -width/2, height/2 }
local shipMotorMaterial = { density = 1.0, friction = 1.0, bounce = 0.0 , shape = shipMotor}
physics.addBody( _spaceShip, shipShapeMaterial, shipMotorMaterial )
return _spaceShip
end
function spaceShip:log()
print("ship")
end
function spaceShip:applyFrontImpulse()
local angle = math.rad(self.rotation)
local xComp, yComp = math.cos(angle), -math.sin(angle)
local forceMag = 2
self:applyLinearImpulse(forceMag * xComp, forceMag * yComp, self.x, self.y)
end
和main.lua的一部分
and part of main.lua
require('camera')
require('gameConf')
require('meteor')
require('spaceShip')
-- Add Physics
local physics = require( "physics" )
physics.start()
physics.setDrawMode( "hybrid" )
physics.setGravity( 0, 0 )
-- Load camera
local camera = camera:New()
-- Containers
meteorManager = {}
shipManager = {}
-- Load Vector class
vector = require "vector"
-- Create one ship
local myShip = nil;
myShip = {}
myShip = spaceShip:New(600, 200, 30, 60)
table.insert(shipManager, myShip)
camera:insert(myShip)
myShip:log() <----- HERE IS THE ERROR
rest of the code...
终端中的错误是:
2013-03-21 19:18:15.736 Corona Simulator[48347:707] Runtime error:
2013-03-21 19:18:15.737 Corona Simulator[48347:707] ...t/iOS/Deep Space Harvest/Deep Space Harvest/main.lua:28: attempt to call method 'log' (a nil value)
stack traceback:
[C]: in function 'log'
...t/iOS/Deep Space Harvest/Deep Space Harvest/main.lua:28: in main chunk
推荐答案
我怀疑问题是由于此片段引起的:
I suspect the issue is because of this fragment:
_spaceShip = {}
setmetatable(_spaceShip, spaceShip)
_spaceShip = display.newRect(posX - width/2, posY - height/2, width, height)
您在_spaceShip
上设置了一个元表,但随后为其分配了一个新值.那时,您分配的新值不具有您在该值(不是变量)上建立的元表关联.
You set a metatable on _spaceShip
, but then assigned a new value to it. At that point the new value you assigned doesn't have the metatable association you established as it's on the value (not variable).
在_spaceShip = display.newRect...
之后移动setmetatable
.
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