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Pogoji in poslovna pravila

Source: tests/schemas/03-guards.orb

Guards are conditions that must be true for a transition to fire. They act as the gatekeepers of your business rules — written once, enforced everywhere, for both the UI and the API.

OrderLifecycleFulfillment/orders/track
Orbital Unit = Entity + Traits + Pages

Kaj je pogoj?​

A guard is an S-expression on a transition. If it evaluates to false, the transition is blocked:

{
  "from": "active",
  "event": "WITHDRAW",
  "to": "active",
  "guard": [">=", "@entity.balance", "@payload.amount"],
  "effects": [...]
}

The user can only withdraw if balance >= amount. If not, the transition is silently blocked (the UI can surface a disabled state or error message).

Sintaksa S-izrazov​

Guards are written as nested arrays where the first element is the operator:

[operator, arg1, arg2, ...]

Arguments can be:

  • Literals: 100, "active", true
  • Bindings: "@entity.field", "@payload.field", "@state", "@now"
  • Nested expressions: ["+", "@entity.count", 1]

Primerjalni operatorji​

OperatorMeaningExample
=Equal["=", "@entity.status", "active"]
!=Not equal["!=", "@entity.role", "guest"]
>Greater than[">", "@entity.score", 0]
>=Greater or equal[">=", "@entity.balance", "@payload.amount"]
<Less than["<", "@entity.attempts", 3]
<=Less or equal["<=", "@entity.age", 65]

Logicni operatorji​

Combine conditions with and, or, not:

["and",
  [">=", "@entity.balance", "@payload.amount"],
  ["=", "@entity.isVerified", true]
]
["or",
  ["=", "@entity.role", "admin"],
  ["=", "@entity.role", "manager"]
]
["not", ["=", "@entity.status", "frozen"]]

Celoten primer: upravljalnik racunov​

This is the complete AccountManager from 03-guards.orb. It demonstrates:

  • A guard using and to combine two conditions
  • Using @payload.amount to check against user input
  • Simple state transitions (freeze/unfreeze) without guards
orbital AccountManager {
  entity Account [persistent: accounts] {
    id : string!
    balance : number
    isVerified : boolean
  }
  trait AccountActions -> Account [interaction] {
    initial: active
    state active {
      INIT -> active
        (fetch Account)
        (render-ui main { type: "entity-table", entity: "Account", fields: ["balance", "isVerified"], columns: ["balance", "isVerified"], itemActions: [{ event: "WITHDRAW", label: "Withdraw" }, { event: "FREEZE", label: "Freeze" }] })
      WITHDRAW -> active
        when (and (>= @entity.balance @payload.amount) (= @entity.isVerified true))
        (set @entity.balance (- @entity.balance @payload.amount))
      FREEZE -> frozen
    }
    state frozen {
      UNFREEZE -> active
    }
  }
  page "/accounts" -> AccountActions
}

Reading the WITHDRAW guard:

["and",
  [">=", "@entity.balance", "@payload.amount"],  // Account has enough funds
  ["=", "@entity.isVerified", true]              // Account is verified
]

Both conditions must be true. If the account is unverified, or the balance is too low, the withdrawal is blocked.

Pogoji z izracenimi vrednostmi​

Guards can use arithmetic operators — the result of a nested expression is used as an argument:

// Only allow if balance after withdrawal stays above minimum
[">=",
  ["-", "@entity.balance", "@payload.amount"],
  100
]
// Only allow if item count is within limit
["<",
  ["+", "@entity.itemCount", 1],
  50
]

Pogosti vzorci pogojev​

Dostop na osnovi vlog​

// Only admins can delete
{
  "from": "listing",
  "event": "DELETE",
  "to": "listing",
  "guard": ["=", "@currentUser.role", "admin"],
  "effects": [["persist", "delete", "Task", "@entity.id"]]
}

Preverjanje lastnistva​

// Only the assignee can start the task
{
  "from": "Pending",
  "event": "START",
  "to": "InProgress",
  "guard": ["=", "@entity.assigneeId", "@currentUser.id"],
  "effects": [["persist", "update", "Task", "@entity"]]
}

Preverjanje polj​

// Score must be between 0 and 100
{
  "guard": ["and",
    [">=", "@payload.score", 0],
    ["<=", "@payload.score", 100]
  ]
}

Predpogoj statusa​

// Can only approve if currently in review
{
  "guard": ["=", "@entity.status", "review"]
}

Pogoji v primerjavi z ucinki​

Guards run before the transition. Effects run after. Never use effects to enforce business rules — that's what guards are for.

// ❌ Wrong: using effects to simulate a guard
"effects": [
  ["if", ["<", "@entity.balance", 0], ["notify", "error", "Insufficient funds"]]
]

// ✅ Correct: guard blocks the transition entirely
"guard": [">=", "@entity.balance", "@payload.amount"]

Naslednji koraki​