when-to-use-a-pointer

1. Updating State
2. Optimize memory for large object that are getting called A LOT

Passing by Reference vs Value

Objects passed by value in a function are COPIED for the lifetime of the function. Any changes made inside the function do not apply to the object that was passed in.

struct Apple {
	Bites int
}
 
func biteApple(a Apple) {
	a.Bites += 1
}
 
demo := Apple{Bites: 0}
biteApple(demo)
 
fmt.Println(demo.bites)

What’s printed?

0

This tripped me up for a minute. Remember…

Objects passed by value in a function are COPIED for the lifetime of the function. Any changes made inside the function do not apply to the object that was passed in.

So what’s the fix? “use a pointer” to pass the value by reference instead of by value.

func biteApple(a *Apple) { // Notice the `*`?
	a.Bites += 1
}
 
/// ----
 
struct Apple {
	Bites int
}
 
func biteApple(a Apple) {
	a.Bites += 1
}
 
demo := Apple{Bites: 0}
biteApple(demo)
 
fmt.Println(demo.bites)

What’s printed?

1