Structs in Blockchain / Solidity - Step-by-Step Execution

Concept Flow - Structs

Define Struct with fields

↓

Create instance of Struct

↓

Access or modify fields

↓

Use struct instance in code

↓

End

Structs group related data together. You define a struct, create instances, access or change fields, then use them in your program.

Execution Sample

Blockchain / Solidity

struct Person {
  string name;
  uint age;
}

Person alice = Person("Alice", 30);

Defines a Person struct with name and age, then creates an instance named alice.

Execution Table

Step	Action	Evaluation	Result
1	Define struct Person with fields name and age	No runtime action	Struct type Person created
2	Create instance alice with name='Alice', age=30	Person("Alice", 30)	alice.name = 'Alice', alice.age = 30
3	Access alice.name	alice.name	'Alice'
4	Access alice.age	alice.age	30
5	Modify alice.age to 31	alice.age = 31	alice.age = 31
6	Use alice in function or logic	Use alice fields	Data from alice used
7	End of execution	No further steps	Execution stops

💡 Reached end of code execution

Variable Tracker

Variable	Start	After Step 2	After Step 5	Final
alice.name	undefined	Alice	Alice	Alice
alice.age	undefined	30	31	31

Key Moments - 3 Insights

Why do we need to define a struct before creating instances?

The struct defines the shape and types of data fields. Without it, the program doesn't know what data each instance should hold (see execution_table step 1).

Can we change the fields of a struct instance after creation?

Yes, struct fields can be modified after creation as shown in execution_table step 5 where alice.age changes from 30 to 31.

How do we access data inside a struct?

We use dot notation like alice.name or alice.age to get or set values, shown in steps 3 and 4 of the execution_table.

Visual Quiz - 3 Questions

Look at the execution_table, what is alice.age after step 5?

A undefined

B 30

C 31

D Alice

💡 Hint

Check variable_tracker row for alice.age after Step 5

At which step is the struct Person defined?

A Step 1

B Step 3

C Step 2

D Step 5

💡 Hint

Look at execution_table step descriptions

If we did not define the struct first, what would happen when creating alice?

A Instance created with default fields

B Error because struct type is unknown

C Fields automatically inferred

D alice.age would be zero

💡 Hint

Refer to key_moments about struct definition necessity

Concept Snapshot

Structs group related data fields.
Define struct with field types.
Create instances with values.
Access or modify fields with dot notation.
Use instances in your code.
Structs help organize complex data.

Full Transcript

Structs are like blueprints for data. First, you define a struct with named fields and their types. Then you create an instance by giving values to those fields. You can access or change these fields using dot notation, like alice.name or alice.age. This helps keep related data together and easy to manage. The execution table shows defining the struct, creating an instance alice with name 'Alice' and age 30, accessing fields, modifying age to 31, and using the instance in code. Variables track how alice's fields change over time. Key moments clarify why defining the struct first is necessary, how to access fields, and that fields can be changed after creation. The quiz tests understanding of these steps and concepts.