Struct usage patterns in Go - Step-by-Step Execution

Concept Flow - Struct usage patterns

Define struct type

↓

Create struct instance

↓

Access or modify fields

↓

Use struct in functions or methods

↓

Pass struct by value or pointer

↓

Update or read fields

↓

End or reuse struct

This flow shows how to define a struct, create instances, access fields, and use structs in functions or methods, including passing by value or pointer.

Execution Sample

Go

package main

type Person struct {
    Name string
    Age  int
}

func main() {
    p := Person{Name: "Alice", Age: 30}
    p.Age = 31
}

Defines a Person struct, creates an instance, and updates the Age field.

Execution Table

Step	Action	Code Line	Variable State	Output/Result
1	Define struct type Person	type Person struct {...}	Person type created	No output
2	Create instance p with Name 'Alice' and Age 30	p := Person{Name: "Alice", Age: 30}	p = {Name: "Alice", Age: 30}	No output
3	Access and modify p.Age to 31	p.Age = 31	p = {Name: "Alice", Age: 31}	No output
4	End of main function	}	p = {Name: "Alice", Age: 31}	Program ends

💡 Program ends after main function completes

Variable Tracker

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

Key Moments - 2 Insights

Why do we use pointers to structs instead of values sometimes?

Using pointers allows functions to modify the original struct fields, as shown in the flow where passing by pointer lets changes persist outside the function. Value passing copies the struct, so changes inside functions don't affect the original.

Can we access struct fields directly after creating an instance?

Yes, as shown in step 3 of the execution_table, you can access and modify fields directly using dot notation like p.Age.

Visual Quiz - 3 Questions

Look at the execution_table, what is the value of p after step 2?

A {Name: "Alice", Age: 30}

B {Name: "Alice", Age: 31}

C undefined

D nil

💡 Hint

Check the 'Variable State' column for step 2 in execution_table

At which step does the Age field of p change?

A Step 1

B Step 2

C Step 3

D Step 4

💡 Hint

Look at the 'Action' and 'Variable State' columns in execution_table

If we passed p by value to a function and modified Age inside, what would happen?

A Original p.Age changes

B Original p.Age stays the same

C Program crashes

D Age field is deleted

💡 Hint

Refer to key_moments about pointer vs value passing

Concept Snapshot

Struct usage patterns in Go:
- Define struct with type keyword
- Create instances with field names
- Access/modify fields with dot notation
- Pass structs by value or pointer
- Pointer passing allows modifying original
- Value passing copies struct, no original change

Full Transcript

This visual execution shows how to use structs in Go. First, we define a struct type named Person with fields Name and Age. Then, we create an instance p with Name 'Alice' and Age 30. Next, we access and modify the Age field to 31 using dot notation. The variable tracker shows how p changes from undefined to the new values. Key moments clarify why pointers are used to modify structs in functions and confirm direct field access. The quiz tests understanding of variable states and passing behavior. The snapshot summarizes the main points for quick review.