CODEWITHSUNDEEP
pointersstructgo
kuang
kuang

Reputation: 727

Difference between Golang struct literals & pointers when accessing struct fields

I don't understand the difference between a struct literal and a struct pointer when accessing struct fields. Is there any different internal behavior ?

type Person struct {
    Name string
}

p := &Person{Name: "Alice"}
u := Person{Name: "Bob"}

fmt.Println(p.Name)  // any difference ?
fmt.Println(u.Name)  // any difference ?

I searched for this but posts I found all explain about difference between value & pointer, or "passing a value" vs "passing a pointer" to a method. They are not what I want to know.

Upvotes: 5

Views: 2065

Answers (1)

Kerrek SB
Kerrek SB

Reputation: 477504

u is a variable of type Person. p is a variable of type "pointer to Person", and it is initialized with the address of an anonymous ("temporary") object. The expression p.Name uses auto-dereferencing of pointers and is equivalent to (*p).Name. The object that p points to lives as long as p points to it and may thereafter be destroyed by Go's non-deterministic memory manager.

Both p.Name and u.Name are expressions of type string, and they're not "passed by pointer" since their address is not taken in the call. In the case of fmt.Println, the value is actually passed "by interface" using Go's structural subtyping form of ad-hoc polymorphism.

Upvotes: 11

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