JSON Examples and Troubleshooting

Real-world recipes for the JSON nodes, plus tips and fixes for common problems.

The examples on this page use a shorthand for Blueprint graphs: each → is the output of one node feeding into the next, and - marks the JSON String input that comes from the previous node.

Examples

Save Player Data

Build a save object, then write it to disk with the File IO nodes.

SaveData = ""
  → Add Field(String, -, "playerName", PlayerName)
  → Add Field(Number, -, "level", LevelAsString)
  → Add Field(Number, -, "health", HealthAsString)
  → Add Field(Number, -, "maxHealth", MaxHealthAsString)
  → Add Array Field(String Array, -, "inventory", InventoryItems)

Save Text To File(Project Saved Directory, "SaveGames/save_slot_1.json", SaveData)

Load Player Data

Read the file back, validate it, then pull out each value.

Load File To String(Project Saved Directory, "SaveGames/save_slot_1.json") → JSONString

if Is Valid JSON(JSONString):
    Get String Field(JSONString, "playerName") → PlayerName
    Get Number Field(JSONString, "level") → Level
    Get Number Field(JSONString, "health") → Health
    Get Array Field(String Array, JSONString, "inventory") → Inventory

Build a Nested Structure

A character sheet with nested equipment objects.

// Build equipment
Weapon = ""
  → Add Field(String, -, "name", "Excalibur")
  → Add Field(Number, -, "damage", "50")
  → Add Field(String, -, "type", "Sword")

Armor = ""
  → Add Field(String, -, "name", "Plate Mail")
  → Add Field(Number, -, "defense", "30")

// Build character
Character = ""
  → Add Field(String, -, "name", "Sir Lancelot")
  → Add Field(Number, -, "level", "20")
  → Add Object Field(-, "weapon", Weapon)
  → Add Object Field(-, "armor", Armor)

The result, formatted for readability:

{
  "name": "Sir Lancelot",
  "level": 20,
  "weapon": {
    "name": "Excalibur",
    "damage": 50,
    "type": "Sword"
  },
  "armor": {
    "name": "Plate Mail",
    "defense": 30
  }
}

Work with Arrays of Objects

A leaderboard built from player objects, then read back in a loop.

// Create player entries
Player1 = ""
  → Add Field(String, -, "name", "Alice")
  → Add Field(Number, -, "score", "100")

Player2 = ""
  → Add Field(String, -, "name", "Bob")
  → Add Field(Number, -, "score", "150")

// Create leaderboard
Leaderboard = ""
  → Add Array Field(Object Array, -, "players", [Player1, Player2])

// Later: read it back
Get Array Field(Object Array, Leaderboard, "players") → PlayerStrings

For Each PlayerString in PlayerStrings:
    Get String Field(PlayerString, "name") → Name
    Get Number Field(PlayerString, "score") → Score
    Print String: Name + " scored " + Score

Tips and Best Practices

• Always validate external JSON. If JSON comes from files, web APIs, or user input, check it with Is Valid JSON first.
• Use Pretty Print for debugging. When things aren't working, run your JSON through Pretty Print JSON and print it to the screen. You'll instantly see what your data looks like.
• Start simple, then nest. Build your JSON from the inside out: create the inner objects first, then nest them in the outer ones.
• Remember that everything is strings. When creating JSON, all values go in as strings and the nodes convert them based on type. When reading number arrays, values come back as strings.
• Check that fields exist. Use Has Field before the getter nodes when you're working with data that might be incomplete.
• Chain your nodes. The output of one creation node feeds right into the next. Start with an empty string, then chain the adds.
• Use the File IO nodes to save and load. The JSON nodes only work with strings. The File IO nodes handle reading and writing them to disk.
• Don't forget object arrays. The Object Array type is perfect for lists of complex items, like inventory, enemies, or quests.

Troubleshooting

My JSON looks weird

• Run it through Pretty Print JSON and print it to see the structure.
• Make sure you're chaining each node's JSON String Out into the next node's JSON String.

A getter node returns false

• Check that the field exists with Has Field.
• Validate the JSON with Is Valid JSON.
• Make sure the field name matches exactly. Field names are case-sensitive.
• Get Array Field and Get Object Field also return false if the field exists but isn't the expected type.

My data disappeared after an add node

• If the JSON String input isn't a valid JSON object, the add nodes start over with an empty object. Check the input with Is Valid JSON.

Numbers aren't working right

• When reading number arrays, values come back as strings like "100.0".
• When creating, make sure you've picked the Number type, not String.
• Empty or non-numeric strings become 0.

My nested objects are broken

• Build inner objects completely before nesting them.
• Use Get Object Field to extract nested JSON, then parse the result again.

My array is empty

• Check that you're using the right Array Type when reading. For example, an Object Array skips elements that aren't objects.
• Verify the array exists with Has Field.
• Make sure the JSON is valid.