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Module 0x2::object_bag

Similar to iota::bag, an ObjectBag is a heterogeneous map-like collection. But unlike iota::bag, the values bound to these dynamic fields must be objects themselves. This allows for the objects to still exist in storage, which may be important for external tools. The difference is otherwise not observable from within Move.

use 0x1::option;
use 0x2::dynamic_object_field;
use 0x2::object;
use 0x2::tx_context;

Resource ObjectBag​

struct ObjectBag has store, key
Fields
id: object::UID

the ID of this bag

size: u64

the number of key-value pairs in the bag

Constants​

const EBagNotEmpty: u64 = 0;

Function new​

Creates a new, empty bag

public fun new(ctx: &mut tx_context::TxContext): object_bag::ObjectBag
Implementation
public fun new(ctx: &mut TxContext): ObjectBag {
ObjectBag {
id: object::new(ctx),
size: 0,
}
}

Function add​

Adds a key-value pair to the bag bag: &mut ObjectBag Aborts with iota::dynamic_field::EFieldAlreadyExists if the bag already has an entry with that key k: K.

public fun add<K: copy, drop, store, V: store, key>(bag: &mut object_bag::ObjectBag, k: K, v: V)
Implementation
public fun add<K: copy + drop + store, V: key + store>(bag: &mut ObjectBag, k: K, v: V) {
ofield::add(&mut bag.id, k, v);
bag.size = bag.size + 1;
}

Function borrow​

Immutably borrows the value associated with the key in the bag bag: &ObjectBag. Aborts with iota::dynamic_field::EFieldDoesNotExist if the bag does not have an entry with that key k: K. Aborts with iota::dynamic_field::EFieldTypeMismatch if the bag has an entry for the key, but the value does not have the specified type.

public fun borrow<K: copy, drop, store, V: store, key>(bag: &object_bag::ObjectBag, k: K): &V
Implementation
public fun borrow<K: copy + drop + store, V: key + store>(bag: &ObjectBag, k: K): &V {
ofield::borrow(&bag.id, k)
}

Function borrow_mut​

Mutably borrows the value associated with the key in the bag bag: &mut ObjectBag. Aborts with iota::dynamic_field::EFieldDoesNotExist if the bag does not have an entry with that key k: K. Aborts with iota::dynamic_field::EFieldTypeMismatch if the bag has an entry for the key, but the value does not have the specified type.

public fun borrow_mut<K: copy, drop, store, V: store, key>(bag: &mut object_bag::ObjectBag, k: K): &mut V
Implementation
public fun borrow_mut<K: copy + drop + store, V: key + store>(bag: &mut ObjectBag, k: K): &mut V {
ofield::borrow_mut(&mut bag.id, k)
}

Function remove​

Mutably borrows the key-value pair in the bag bag: &mut ObjectBag and returns the value. Aborts with iota::dynamic_field::EFieldDoesNotExist if the bag does not have an entry with that key k: K. Aborts with iota::dynamic_field::EFieldTypeMismatch if the bag has an entry for the key, but the value does not have the specified type.

public fun remove<K: copy, drop, store, V: store, key>(bag: &mut object_bag::ObjectBag, k: K): V
Implementation
public fun remove<K: copy + drop + store, V: key + store>(bag: &mut ObjectBag, k: K): V {
let v = ofield::remove(&mut bag.id, k);
bag.size = bag.size - 1;
v
}

Function contains​

Returns true iff there is an value associated with the key k: K in the bag bag: &ObjectBag

public fun contains<K: copy, drop, store>(bag: &object_bag::ObjectBag, k: K): bool
Implementation
public fun contains<K: copy + drop + store>(bag: &ObjectBag, k: K): bool {
ofield::exists_<K>(&bag.id, k)
}

Function contains_with_type​

Returns true iff there is an value associated with the key k: K in the bag bag: &ObjectBag with an assigned value of type V

public fun contains_with_type<K: copy, drop, store, V: store, key>(bag: &object_bag::ObjectBag, k: K): bool
Implementation
public fun contains_with_type<K: copy + drop + store, V: key + store>(bag: &ObjectBag, k: K): bool {
ofield::exists_with_type<K, V>(&bag.id, k)
}

Function length​

Returns the size of the bag, the number of key-value pairs

public fun length(bag: &object_bag::ObjectBag): u64
Implementation
public fun length(bag: &ObjectBag): u64 {
bag.size
}

Function is_empty​

Returns true iff the bag is empty (if length returns 0)

public fun is_empty(bag: &object_bag::ObjectBag): bool
Implementation
public fun is_empty(bag: &ObjectBag): bool {
bag.size == 0
}

Function destroy_empty​

Destroys an empty bag Aborts with EBagNotEmpty if the bag still contains values

public fun destroy_empty(bag: object_bag::ObjectBag)
Implementation
public fun destroy_empty(bag: ObjectBag) {
let ObjectBag { id, size } = bag;
assert!(size == 0, EBagNotEmpty);
id.delete()
}

Function value_id​

Returns the ID of the object associated with the key if the bag has an entry with key k: K Returns none otherwise

public fun value_id<K: copy, drop, store>(bag: &object_bag::ObjectBag, k: K): option::Option<object::ID>
Implementation
public fun value_id<K: copy + drop + store>(bag: &ObjectBag, k: K): Option<ID> {
ofield::id(&bag.id, k)
}