Struct pointers in Go - Step-by-Step Execution

Concept Flow - Struct pointers

Declare struct type

↓

Create struct instance

↓

Create pointer to struct

↓

Access/modify fields via pointer

↓

Use updated struct values

This flow shows how to declare a struct, create an instance, get a pointer to it, and access or change its fields through the pointer.

Execution Sample

Go

package main
import "fmt"

type Person struct {
    Name string
    Age  int
}

func main() {
    p := Person{"Alice", 30}
    pPtr := &p
    pPtr.Age = 31
    fmt.Println(p.Age)
}

This code creates a Person struct, gets a pointer to it, changes Age via the pointer, and prints the updated Age.

Execution Table

Step	Action	Variable	Value	Explanation
1	Declare struct type Person	Person	struct {Name string; Age int}	Defines a new struct type with Name and Age fields
2	Create instance p	p	Person{Name:"Alice", Age:30}	p holds a Person with Name Alice and Age 30
3	Create pointer pPtr to p	pPtr	&p	pPtr points to the memory address of p
4	Modify Age via pointer	pPtr.Age	31	Changes Age field of p through pPtr to 31
5	Print p.Age	Output	31	Shows updated Age value after modification
6	End			Program ends after printing updated Age

💡 Program ends after printing the updated Age value 31

Variable Tracker

Variable	Start	After Step 2	After Step 3	After Step 4	Final
p	undefined	Person{Name:"Alice", Age:30}	Person{Name:"Alice", Age:30}	Person{Name:"Alice", Age:31}	Person{Name:"Alice", Age:31}
pPtr	undefined	undefined	&p	&p	&p

Key Moments - 2 Insights

Why does changing pPtr.Age also change p.Age?

Because pPtr points to p's memory, modifying pPtr.Age changes the actual data in p, as shown in step 4 and confirmed by the output in step 5.

Can we access struct fields directly through a pointer without explicit dereferencing?

Yes, Go lets you use pPtr.Age instead of (*pPtr).Age, making code simpler. This is shown in step 4.

Visual Quiz - 3 Questions

Look at the execution table, what is the value of p.Age after step 4?

A 30

B 0

C 31

D undefined

💡 Hint

Check the 'Value' column for variable p after step 4 in the execution_table.

At which step is the pointer pPtr created?

A Step 3

B Step 4

C Step 2

D Step 1

💡 Hint

Look for the action 'Create pointer pPtr to p' in the execution_table.

If we changed pPtr.Age to 35 instead of 31, what would be printed at step 5?

A 31

B 35

C 30

D Error

💡 Hint

Changing pPtr.Age updates p.Age because pPtr points to p, see variable_tracker changes.

Concept Snapshot

Struct pointers in Go:
- Define struct type: type Name struct { fields }
- Create instance: var v = Name{...}
- Get pointer: p := &v
- Access fields via pointer: p.Field (no * needed)
- Modifying via pointer changes original struct
- Useful for efficient data handling

Full Transcript

This example shows how to use pointers to structs in Go. First, we define a struct type Person with Name and Age fields. Then, we create an instance p with Name Alice and Age 30. Next, we create a pointer pPtr that points to p. Using pPtr, we change the Age field to 31. Because pPtr points to p, this change updates p's Age as well. Finally, printing p.Age shows the updated value 31. This demonstrates how struct pointers let us modify the original data efficiently.