[英]LUA and Corona error: Attempt To Call Method ' ' (A Nil Value) - Driving Me Crazy
我會請求你的幫助,因為一個讓我瘋狂的錯誤。
哦......我正在使用LUA和Corona SDK btw ......
我正在創建一個船的實例。 該船正在實例化,我可以訪問其屬性,但我無法訪問任何方法! 按照代碼,我不知道該怎么做:
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
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...
終端中的錯誤是:
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
我懷疑這個問題是因為這個片段:
_spaceShip = {}
setmetatable(_spaceShip, spaceShip)
_spaceShip = display.newRect(posX - width/2, posY - height/2, width, height)
您在_spaceShip
上設置了metatable,但隨后_spaceShip
分配了一個新值。 此時,您指定的新值沒有您建立的metatable關聯,因為它在值(非變量)上。
在_spaceShip = display.newRect...
之后移動setmetatable
。
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