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2. Designing Subjects

In this tutorial, we will design the subjects for our personal tree application. We will define the states and behaviors that will dictate how our virtual tree grows and interacts with users.

Step 1: Understanding Subjects​

In Subjektify, a subject is a core component that defines a specific entity within your application. Each subject can have states (attributes), behaviors (functions), and relationships with other subjects.

Step 2: Define the Tree Subject​

We will start by defining a Tree subject. This subject will have states like age, height, and health, and behaviors like grow, water, and fertilize.

Create the Tree.subjekt File​

Create a new file named Tree.subjekt inside the subjects directory.

cd subjects
touch Tree.subjekt

Define the Tree Subject​

First, we define the Tree subject with its states and behaviors.

Tree.subjekt
subject Tree {
    states: [
        TreeState
    ]
    behaviors: [
        Grow,
        Water,
        Plant
    ]
}

Define the Tree State​

Define the states for the Tree subject.

Tree.subjekt
state TreeState {
    id: string
    age: int
    height: float
    health: string
}

Define the Grow Behavior​

Define the behavior for growing the tree.

Tree.subjekt
behavior Grow {
    inputs: [
        {
            name: "growthAmount",
            type: float
        }
    ]
    outputs: [
        {
            name: "newHeight",
            type: float
        }
    ]
    triggers: []
}

Define the Planting Behavior​

Define the behavior for planting the tree.

Tree.subjekt
behavior Plant {
    inputs: []
    outputs: [
        {
            name: "health",
            type: string
        }
    ]
    triggers: []
}

Define the Water Behavior​

Define the behavior for watering the tree.

Tree.subjekt
behavior Water {
    inputs: []
    outputs: [
        {
            name: "health",
            type: string
        }
    ]
    triggers: []
}

Complete Tree.subjekt File​

Here is the complete Tree.subjekt file:

Tree.subjekt
metadata {
    version = "0.1.0"
    license = "MIT"
    author = "Your Name"
}

use "subjektify.base#State"
use "subjektify.base#Behavior"

subject Tree {
    states: [
        TreeState
    ]
    behaviors: [
        Grow,
        Water,
        Plant
    ]
}

state TreeState {
    id: string
    age: int
    height: float
    health: string
}

behavior Grow {
    inputs: [
        {
            name: "growthAmount",
            type: float
        }
    ]
    outputs: [
        {
            name: "newHeight",
            type: float
        }
    ]
    triggers: []
}

behavior Water {
    inputs: []
    outputs: [
        {
            name: "health",
            type: string
        }
    ]
    triggers: []
}

behavior Plant {
    inputs: []
    outputs: [
        {
            name: "health",
            type: string
        }
    ]
    triggers: []
}

Step 3: Verify Your Subject Definition​

To ensure that your subject definition is correct, use the Subjektify CLI to verify the Tree.subjekt file in your root directory:

npx subjektify verify

Next Steps​

You have now defined the Tree subject with its states and behaviors. In the next tutorial, we will cover testing subjects to ensure that they function as expected.