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Classes & Object-Oriented Programming

Classes in Kyna encapsulate data fields with behavior, providing structured data modeling for services, database models, and domain entities.

1. Defining a Class​

Classes are declared with class and initialized with a constructor method named init:

class DatabaseConfig {
    public init(host: str, port: int, database: str) {
        self.host = host;
        self.port = port;
        self.database = database;
        self.maxConnections = 10;
    }

    fn getConnectionString(): str {
        return "postgres://" + self.host + ":" + self.port + "/" + self.database;
    }
}

const config = DatabaseConfig("db.internal", 5432, "production");
print(config.getConnectionString());
# Output: postgres://db.internal:5432/production

2. Methods and Member Fields​

Inside class methods, use self to access member variables and call sibling methods:

class RateLimiter {
    public init(maxTokens: int) {
        self.maxTokens = maxTokens;
        self.currentTokens = maxTokens;
    }

    fn allowRequest(): bool {
        if (self.currentTokens > 0) {
            self.currentTokens = self.currentTokens - 1;
            return true;
        }
        return false;
    }

    fn refill(tokens: int) {
        self.currentTokens = self.currentTokens + tokens;
        if (self.currentTokens > self.maxTokens) {
            self.currentTokens = self.maxTokens;
        }
    }
}

var limiter = RateLimiter(2);
print("Req 1:", limiter.allowRequest()); # true
print("Req 2:", limiter.allowRequest()); # true
print("Req 3:", limiter.allowRequest()); # false (Rate limit exceeded)

limiter.refill(1);
print("Req 4 after refill:", limiter.allowRequest()); # true

3. Interfaces & Contracts​

Define interfaces to enforce consistent contracts across different class implementations:

interface Serializer {
    fn serialize(): str;
}

class UserRecord implements Serializer {
    public init(id: int, username: str) {
        self.id = id;
        self.username = username;
    }

    fn serialize(): str {
        return jsonStringify({
            "id": self.id,
            "username": self.username
        });
    }
}

Next Steps​