Conditional Actions

Conditional actions allow a route to execute different sets of actions based on runtime conditions. They use an if/else syntax within the action list.

Syntax

if condition => [
    // actions when true
] else [
    // actions when false
]

The else branch is optional:

if condition => [
    // actions when true
]

Basic Usage

Execute an action only when a condition is met:

routes {
    withdraw(amount: U256) => [
        if amount > 0 => [
            ~> msg::sender with { value: amount }
        ]
    ]
}

If/Else

Choose between two action sequences:

routes {
    process(amount: U256) => [
        if amount >= m_threshold => [
            LargeTransfer(amount) ~> m_compliance,
            ~> msg::sender with { value: amount }
        ] else [
            ~> msg::sender with { value: amount }
        ]
    ]
}

Conditions

The condition can be any boolean expression:

Comparisons

if m_balance >= amount => [
    ~> recipient with { value: amount }
]

Macro Calls

if @is_owner() => [
    ~> m_treasury with { value: m_balance }
]

Member State

if m_status == Status::Active => [
    Process(data) ~> m_processor
] else [
    Queue(data) ~> m_queue
]

Compound Conditions

if amount > 0 && m_balance >= amount => [
    ~> msg::sender with { value: amount }
]

Nested Conditionals

Conditional actions can be nested for multi-branch logic:

routes {
    categorize(score: u64) => [
        if score >= 90 => [
            Award("gold") ~> m_rewards
        ] else [
            if score >= 70 => [
                Award("silver") ~> m_rewards
            ] else [
                Award("bronze") ~> m_rewards
            ]
        ]
    ]
}

Conditional Sends

A common pattern is conditionally sending a refund:

routes {
    bid()
        where msg::value > m_highest_bid : throw 100
    => [
        if m_highest_bid > 0 => [
            ~> m_highest_bidder with { value: m_highest_bid }
        ]
    ]
}

This refunds the previous highest bidder only if there was a previous bid.

Conditional Deploy

Deploy an entity only under certain conditions:

routes {
    ensure_vault(user: address) => [
        if m_vaults.exists(user) == false => [
            deploy UserVault(user) with { value: 1_000_000 }
        ]
    ]
}

Conditionals with Let Bindings

Let bindings can precede conditional actions:

routes {
    distribute(total: U256) => [
        let fee = total * 3 / 100;
        let net = total - fee;
        if fee > 0 => [
            ~> m_treasury with { value: fee }
        ],
        ~> m_recipient with { value: net }
    ]
}

Complete Example

entity Escrow {
    routes {
        resolve(approved: bool)
            where msg::sender == m_arbiter : throw 200
        => [
            if approved => [
                ~> m_seller with { value: m_amount },
                Resolved(m_deal_id, true) ~> m_logger
            ] else [
                ~> m_buyer with { value: m_amount },
                Resolved(m_deal_id, false) ~> m_logger
            ]
        ]
    }
}