Defining structs in Go - Step-by-Step Execution

Concept Flow - Defining structs

Start

↓

Define struct type

↓

Create struct variable

↓

Assign values to fields

↓

Use struct variable

↓

End

This flow shows how you define a struct type, create a variable of that type, assign values to its fields, and then use it.

Execution Sample

Go

package main

type Person struct {
    Name string
    Age  int
}

func main() {
    var p Person
    p.Name = "Alice"
    p.Age = 30
}

Defines a struct Person with fields Name and Age, creates a variable p, and assigns values to its fields.

Execution Table

Step	Action	Evaluation	Result
1	Define struct type Person	Person struct with fields Name(string), Age(int)	Type Person created
2	Declare variable p of type Person	p is zero-valued Person	p.Name = "", p.Age = 0
3	Assign p.Name = "Alice"	Set field Name	p.Name = "Alice"
4	Assign p.Age = 30	Set field Age	p.Age = 30
5	Use p (e.g., print)	Access fields	Outputs: Name: Alice, Age: 30

💡 All steps completed, struct variable p fully initialized and used

Variable Tracker

Variable	Start	After Step 2	After Step 3	After Step 4	Final
p.Name	""	""	"Alice"	"Alice"	"Alice"
p.Age	0	0	0	30	30

Key Moments - 3 Insights

Why does p.Name start as an empty string before assignment?

In step 2 of the execution_table, p is declared but not assigned, so Go sets string fields to their zero value, which is an empty string.

Can I assign values to struct fields before declaring the variable?

No, as shown in step 3 and 4, you must declare the variable (step 2) before assigning values to its fields.

What happens if I forget to assign a field value?

That field keeps its zero value, like p.Age would stay 0 if not assigned, as seen in step 2.

Visual Quiz - 3 Questions

Look at the variable_tracker, what is the value of p.Age after Step 3?

A 30

B 0

C "Alice"

D undefined

💡 Hint

Check the 'After Step 3' column for p.Age in variable_tracker

At which step in execution_table is the struct variable p declared?

A Step 1

B Step 3

C Step 2

D Step 4

💡 Hint

Look for 'Declare variable p' action in execution_table

If you skip assigning p.Name, what would be its final value according to variable_tracker?

A "" (empty string)

B "Alice"

C nil

D 0

💡 Hint

See the 'Start' and 'After Step 2' values for p.Name in variable_tracker

Concept Snapshot

Defining structs in Go:
- Use 'type Name struct { fields }' to define
- Declare variable: 'var v Name'
- Fields have zero values initially
- Assign fields: 'v.Field = value'
- Use struct variable after assignment

Full Transcript

This example shows how to define a struct type named Person with two fields: Name and Age. First, the struct type is created. Then, a variable p of type Person is declared, which initializes its fields to zero values (empty string for Name, 0 for Age). Next, values are assigned to the fields: p.Name is set to "Alice" and p.Age to 30. Finally, the struct variable p can be used, for example, printed to show its field values. The variable tracker shows how p.Name and p.Age change step by step. Key moments clarify why fields start with zero values and the order of declaration and assignment. The quiz tests understanding of variable values at different steps and the effect of skipping assignments.