I'm learning Golang and I come from PHP background. I have a bit of trouble understanding some of the core functionalities at times.
Specifically, right now I'm building a Hearths game and I've created a CardStack type, that has some convenient methods one might use in a card stack (read: player's hand, discard pile...) such as DrawCards(...)
, AppendCards(...)
...
The problem I have is that the function func (c* CardStack) DrawCards(cards []deck.Card) ([]deck.Card, error) {...}
changes the argument cards []deck.Card
and I cannot figure out why or how to avoid this.
This is my CardStack:
type CardStack struct {
cards []deck.Card
}
This is my DrawCards
method:
func (c *CardStack) DrawCards(cards []deck.Card) ([]deck.Card, error) {
return c.getCardsSlice(cards, true)
}
// Returns cards that are missing
func (c *CardStack) getCardsSlice(cards []deck.Card, rm bool) ([]deck.Card, error) {
var err error
var returnc = []deck.Card{}
for _, card := range cards {
fmt.Println("BEFORE c.findCard(cards): ")
deck.PrintCards(cards) // In my example this will print out {Kc, 8d}, which is what I expect it to be
_, err = c.findCard(card, rm) // AFTER THIS LINE THE cards VAR IS CHANGED
fmt.Println("AFTER c.findCard(cards): ")
deck.PrintCards(cards) // In my example this will print out {8d, 8d}, which is not at all what I expected
if err != nil {
return returnc, err
}
}
return returnc, nil
}
// Expects string like "Ts" or "2h" (1. face 2. suit)
func (c *CardStack) findCard(cc deck.Card, rm bool) (deck.Card, error) {
for i, card := range c.GetCards() {
if cc == card {
return c.cardByIndex(i, rm)
}
}
return deck.Card{}, fmt.Errorf("Card not found")
}
func (c *CardStack) cardByIndex(n int, rm bool) (deck.Card, error) {
if n > len(c.GetCards()) {
return deck.Card{}, fmt.Errorf("Index out of bounds")
}
card := c.GetCards()[n]
if rm {
c.SetCards(append(c.GetCards()[:n], c.GetCards()[n+1:]...))
}
return card, nil
}
To explain a bit more - specifically the findCard(...)
method that gets called in getCardsSlice
messes with the original value (I've added comments to indicate where it happens).
If it's of any help, this is part of my main()
method that I use for debugging:
// ...
ss, _ := cards.SubStack(1, 3) // ss now holds {Kc, 8d}
ss.Print() // Prints {Kc, 8d}
cards.Print() // Prints {5c, Kc, 8d} (assigned somewhere up in the code)
cards.DrawCards(ss) // Draws {Kc, 8d} from {5c, Kc, 8d}
cards.Print() // Prints {5c} - as expected
ss.Print() // Prints {8d, 8d} - ???
What am I doing wrong and how should I go about doing this.
Any kind of help is appreciated.
Edit:
The whole CardStack file: http://pastebin.com/LmhryfGc
Edit2:
I was going to put it on github sooner or later (was hoping after the code looks semi-ok), here it is - https://github.com/d1am0nd/hearths-go/tree/cardstack/redo