Introducing Go: Build Reliable, Scalable Programs by Caleb Doxsey

Author:Caleb Doxsey [Doxsey, Caleb]
Language: eng
Format: azw3, pdf
Publisher: O'Reilly Media
Published: 2016-01-07T05:00:00+00:00

func zero(xPtr *int) { *xPtr = 0 } func main() { x := 5 zero(&x) fmt.Println(x) // x is 0 }

Pointers reference a location in memory where a value is stored rather than the value itself. By using a pointer (*int), the zero function is able to modify the original variable.

The * and & operators

In Go, a pointer is represented using an asterisk (*) followed by the type of the stored value. In the zero function, xPtr is a pointer to an int.

An asterisk is also used to dereference pointer variables. Dereferencing a pointer gives us access to the value the pointer points to. When we write *xPtr = 0, we are saying “store the int 0 in the memory location xPtr refers to.” If we try xPtr = 0 instead, we will get a compile-time error because xPtr is not an int; it’s a *int, which can only be given another *int.

Finally, we use the & operator to find the address of a variable. &x returns a *int (pointer to an int) because x is an int. This is what allows us to modify the original variable. &x in main and xPtr in zero refer to the same memory location.

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