JSON serialization in Unity - Mini Project: Build & Apply

JSON serialization

📖 Scenario: You are creating a simple game inventory system in Unity. You want to save the player's inventory data as JSON so it can be saved to a file or sent over the network.

🎯 Goal: Build a Unity C# script that creates an inventory dictionary, sets a configuration for serialization, serializes the dictionary to JSON, and prints the JSON string.

📋 What You'll Learn

Create a dictionary called inventory with exact items and quantities

Create a boolean variable called prettyPrint to control JSON formatting

Serialize the inventory dictionary to a JSON string using JsonUtility or JsonConvert

Print the JSON string to the Unity console

💡 Why This Matters

🌍 Real World

Game developers often save player data like inventory or settings in JSON format for easy storage and transfer.

💼 Career

Understanding JSON serialization is essential for Unity developers working on save systems, multiplayer games, or data exchange.

1

Create the inventory dictionary

Create a dictionary called inventory with these exact entries: "Potion" with quantity 5, "Elixir" with quantity 3, and "Sword" with quantity 1.

Unity

# Create the inventory dictionary with exact items and quantities
# Your code here

Hint

Use Dictionary<string, int> and initialize it with the exact key-value pairs.

2

Add pretty print configuration

Create a boolean variable called prettyPrint and set it to true to enable formatted JSON output.

Unity

using System.Collections.Generic;

Dictionary inventory = new Dictionary()
{
    {"Potion", 5},
    {"Elixir", 3},
    {"Sword", 1}
};

// Create a boolean variable called prettyPrint and set it to true
# Your code here

Hint

Declare a boolean variable named prettyPrint and assign it the value true.

3

Serialize the inventory to JSON

Serialize the inventory dictionary to a JSON string called jsonString using JsonUtility or JsonConvert.SerializeObject with the prettyPrint option.

Unity

using System.Collections.Generic;
using Newtonsoft.Json;

Dictionary inventory = new Dictionary()
{
    {"Potion", 5},
    {"Elixir", 3},
    {"Sword", 1}
};

bool prettyPrint = true;

// Serialize inventory to jsonString using JsonConvert.SerializeObject with prettyPrint
# Your code here

Hint

Use JsonConvert.SerializeObject with the Formatting enum to control pretty printing.

4

Print the JSON string

Write a line to print the jsonString to the Unity console using Debug.Log.

Unity

using System.Collections.Generic;
using Newtonsoft.Json;
using UnityEngine;

Dictionary inventory = new Dictionary()
{
    {"Potion", 5},
    {"Elixir", 3},
    {"Sword", 1}
};

bool prettyPrint = true;

string jsonString = JsonConvert.SerializeObject(inventory, prettyPrint ? Formatting.Indented : Formatting.None);

// Print jsonString to the Unity console
# Your code here

Hint

Use Debug.Log(jsonString); to print the JSON string in Unity's console.

Practice

1.

What is the main purpose of JSON serialization in Unity?

easy

A. Create 3D models from code

B. Convert objects into text format and back

C. Compile scripts faster

D. Optimize game performance automatically

Solution

1. Step 1: Understand JSON serialization

   JSON serialization means turning objects into text so they can be saved or sent.

2. Step 2: Recognize Unity's use

   Unity uses JSON serialization to save object data as text and load it back.

3. Final Answer:

   Convert objects into text format and back -> Option B

4. Quick Check:

   JSON serialization = Convert objects to text and back [OK]

Hint: Think: saving objects as readable text [OK]

Common Mistakes:

• Confusing serialization with 3D modeling
• Thinking it speeds up script compilation
• Assuming it optimizes performance automatically

2.

Which of the following is the correct way to serialize an object player to JSON in Unity?

Player player = new Player();

easy

A. string json = JsonUtility.ToJson(player);

B. string json = Json.Serialize(player);

C. string json = JsonUtility.FromJson(player);

D. string json = player.ToJson();

Solution

1. Step 1: Identify Unity's serialization method

   Unity uses JsonUtility.ToJson() to convert objects to JSON text.

2. Step 2: Check method usage

   JsonUtility.ToJson(player) correctly serializes the player object.

3. Final Answer:

   string json = JsonUtility.ToJson(player); -> Option A

4. Quick Check:

   Serialize with JsonUtility.ToJson() [OK]

Hint: Use JsonUtility.ToJson() to serialize objects [OK]

Common Mistakes:

• Using FromJson() instead of ToJson()
• Calling non-existent Json.Serialize() method
• Trying to call ToJson() on the object itself

3.

Given the following code, what will be the output?

[System.Serializable]
public class Player {
    public string name = "Alex";
    public int score = 10;
}

Player player = new Player();
string json = JsonUtility.ToJson(player);
Debug.Log(json);

medium

A. {"name":"Alex","score":10}

B. {"name":"Alex"}

C. {"score":10}

D. Error: Player class not serializable

Solution

1. Step 1: Check class serialization

   The Player class is marked [System.Serializable], so it can be converted to JSON.

2. Step 2: Understand JsonUtility.ToJson output

   It converts all public fields to JSON key-value pairs, so name and score appear.

3. Final Answer:

   {"name":"Alex","score":10} -> Option A

4. Quick Check:

   Serializable class fields appear in JSON [OK]

Hint: Serializable class fields become JSON keys [OK]

Common Mistakes:

• Forgetting [System.Serializable] attribute
• Expecting private fields to appear
• Thinking only one field is serialized

4.

What is wrong with this code snippet for deserializing JSON into a Player object?

string json = "{\"name\":\"Sam\", \"score\":15}";
Player player = JsonUtility.ToJson(json);

medium

A. JSON string is not properly formatted

B. Player class must be private

C. Using ToJson() instead of FromJson() for deserialization

D. Missing semicolon after JSON string

Solution

1. Step 1: Identify method misuse

   JsonUtility.ToJson() is for serialization, not deserialization.

2. Step 2: Correct method for deserialization

   Use JsonUtility.FromJson<Player>(json) to convert JSON text back to Player object.

3. Final Answer:

   Using ToJson() instead of FromJson() for deserialization -> Option C

4. Quick Check:

   Deserialize with FromJson(), not ToJson() [OK]

Hint: Use FromJson() to convert JSON text to object [OK]

Common Mistakes:

• Mixing ToJson() and FromJson() methods
• Assuming JSON string format is wrong
• Thinking class visibility affects serialization

5.

You want to save a list of Player objects to JSON and load them back later. Which approach correctly handles this in Unity?

hard

A. Serialize the list directly with JsonUtility.ToJson(playersList)

B. Use JsonUtility.FromJson<List<Player>>(json) to deserialize

C. Serialize each Player separately and concatenate JSON strings

D. Wrap the list in a serializable container class and serialize that

Solution

1. Step 1: Understand Unity's JsonUtility limitation

   JsonUtility cannot serialize lists directly; it needs a wrapper class.

2. Step 2: Use a container class

   Create a [System.Serializable] class with a public List<Player> field and serialize that.

3. Final Answer:

   Wrap the list in a serializable container class and serialize that -> Option D

4. Quick Check:

   Wrap lists in container class for JSON serialization [OK]

Hint: Wrap lists in a class before serializing [OK]

Common Mistakes:

• Trying to serialize lists directly
• Concatenating JSON strings manually
• Using FromJson with generic List type