Nullability & no null

There is no null in Redstart. Anything that might be absent is Option<T>, and the compiler forces you to handle the empty case before you touch the value.

entity Account {
  id: Id<Bytes>
  label: Option<String>     // nullable in the generated schema
}

label renders as label: String (nullable) in schema.graphql, while a plain balance: BigInt renders as balance: BigInt! (required).

Why this matters

In hand-written AssemblyScript, arithmetic on a nullable value silently miscompiles, and a forgotten null check aborts the handler at runtime. Redstart makes both compile errors:

• Arithmetic on Option is rejected — you must unwrap first.
• Dereferencing a nullable host return is rejected. store.get-style loads (Entity.load, loadInBlock) and ipfs.cat return Option<T>; you must match them before use:

match Account.load(id) {
  Some(account) => {
    account.balance = account.balance + amount   // matched binding auto-saves
  }
  None => {
    // nothing to update
  }
}

loadOrCreate exists precisely so the common case doesn’t need a match — it always returns a live entity.