删除所有产生的硬币

Question

What is the best way to remove all spawned coins when the game is over?

Here is the code that spawns the coins:

 screenGroup = self.view
 coin = {}
 coinspawn = function()
 i = display.newSprite( imageSheet1, sequenceData1 )

    i.x = display.contentWidth
    i.y = math.random(0, display.contentHeight-50)
    i:play()
    i.collided = true
    i.name = "coin"
    physics.addBody(i, "dynamic", 
        {density=.1, bounce=0.1, friction=.2, shape= shape2 ,filter=playerCollisionFilter } 
    )   
    --player.gravityScale = 0.5
    coinIntro = transition.to(i,{time=2500, x=display.contentWidth - display.contentWidth -500  ,onComplete=jetReady , transition=easing.OutExpo } ) --
    coin[#coin+1] = i

end 
tmrcoin = timer.performWithDelay( 1000, coinspawn, 0 )

Answer 1

First you would remove all coins from the display. Then you would clear the coin table:

for i=1,#coin do 
    coin[i]:removeSelf()
end
coin = {}  -- forget all coins

Assuming coin table is the only other place you store your coins, this will do it.

Note that you can't use coin[i]=nil in the loop after removeSelf : as soon as table has holes, the # operator is basically unusable. You can't use table.remove either, because i gets incremented every time, so you'll miss items (try, you'll see). Same issue with pairs: you can't edit a table while iterating through it. You could however do this:

local numCoins = #coin
for i=1,numCoins do 
    coin[i]:removeSelf()
    coin[i]=nil
end
-- now coin is {}

The only reason I can think of to nil N items instead of letting the gc take care of it with one table = {} statement is if you have more than one reference to your coin table (which I would rename to coins, BTW, for clarity).