Structures and fields

struct Demo {
    allowExotic: bool = false
    customData: tuple
}

fun demo() {
    // the type is clear from the assignment
    var o1: Demo = { customData: someTuple };
    o1.someMethod();

    // alternatively, `Demo { ... }`
    Demo{customData: someTuple}.someMethod();
}

fun createDemo(allowExotic: bool, customData: tuple) {
    return Demo { allowExotic, customData }
}

fun Demo.hasData(self): bool {
    return self.customData.size() != 0
}

struct blockchain

fun blockchain.now(): int
    asm "NOW"

fun blockchain.logicalTime(): int
    asm "LTIME"

struct DefDemo {
    f1: int = 0
    f2: int? = null
    f3: (int, coins) = (0, ton("0.05"))
}

fun demo() {
    var d: DefDemo = {};         // ok
    var d: DefDemo = { f2: 5 };  // ok
}

struct PositionInTuple {
    private readonly t: tuple
    currentIndex: int
}

fun PositionInTuple.create(t: tuple): PositionInTuple {
    return { t, currentIndex: 0 }
}

fun PositionInTuple.next(mutate self) {
    // self.t cannot be modified: it is readonly
    self.currentIndex += 1;
}

fun demo() {
    var p = PositionInTuple.create(someTuple);
    // p.t is unavailable here: it is private
}

struct Nullable<T> {
    value: T?
}

fun Nullable<T>.isNull(self) {
    return self.value == null
}

fun Nullable<map<K, V>>.isNull(self) {
    return self.value.isEmpty()
}

struct (0x7362d09c) TransferNotification {
    queryId: uint64
    // ...
}

// message will be '0x7362d09c0000000000000000' + ...
createMessage({
    // ...
    body: TransferNotification {
        queryId: 0,
        // ...
    }
});