Struct frame_support::storage::types::StorageMap[][src]

pub struct StorageMap<Prefix, Hasher, Key, Value, QueryKind = OptionQuery, OnEmpty = GetDefault, MaxValues = GetDefault>(_);
Expand description

A type that allow to store value for given key. Allowing to insert/remove/iterate on values.

Each value is stored at:

Twox128(Prefix::pallet_prefix())
		++ Twox128(Prefix::STORAGE_PREFIX)
		++ Hasher1(encode(key))

Warning

If the keys are not trusted (e.g. can be set by a user), a cryptographic hasher such as blake2_128_concat must be used. Otherwise, other values in storage can be compromised.

Implementations

Get the storage key used to fetch a value corresponding to a specific key.

Does the value (explicitly) exist in storage?

Load the value associated with the given key from the map.

Try to get the value for the given key from the map.

Returns Ok if it exists, Err if not.

Swap the values of two keys.

Store a value to be associated with the given key from the map.

Remove the value under a key.

Mutate the value under a key.

Mutate the item, only if an Ok value is returned.

Mutate the value under a key. Deletes the item if mutated to a None.

Mutate the item, only if an Ok value is returned. Deletes the item if mutated to a None.

Take the value under a key.

Append the given items to the value in the storage.

Value is required to implement codec::EncodeAppend.

Warning

If the storage item is not encoded properly, the storage will be overwritten and set to [item]. Any default value set for the storage item will be ignored on overwrite.

Read the length of the storage value without decoding the entire value under the given key.

Value is required to implement StorageDecodeLength.

If the value does not exists or it fails to decode the length, None is returned. Otherwise Some(len) is returned.

Warning

None does not mean that get() does not return a value. The default value is completly ignored by this function.

Migrate an item with the given key from a defunct OldHasher to the current hasher.

If the key doesn’t exist, then it’s a no-op. If it does, then it returns its value.

Remove all value of the storage.

Iter over all value of the storage.

NOTE: If a value failed to decode because storage is corrupted then it is skipped.

Translate the values of all elements by a function f, in the map in no particular order.

By returning None from f for an element, you’ll remove it from the map.

NOTE: If a value fail to decode because storage is corrupted then it is skipped.

Warning

This function must be used with care, before being updated the storage still contains the old type, thus other calls (such as get) will fail at decoding it.

Usage

This would typically be called inside the module implementation of on_runtime_upgrade.

Try and append the given item to the value in the storage.

Is only available if Value of the storage implements StorageTryAppend.

Enumerate all elements in the map in no particular order.

If you alter the map while doing this, you’ll get undefined results.

Enumerate all elements in the map after a specified starting_raw_key in no particular order.

If you alter the map while doing this, you’ll get undefined results.

Enumerate all keys in the map in no particular order.

If you alter the map while doing this, you’ll get undefined results.

Enumerate all keys in the map after a specified starting_raw_key in no particular order.

If you alter the map while doing this, you’ll get undefined results.

Remove all elements from the map and iterate through them in no particular order.

If you add elements to the map while doing this, you’ll get undefined results.

Translate the values of all elements by a function f, in the map in no particular order.

By returning None from f for an element, you’ll remove it from the map.

NOTE: If a value fail to decode because storage is corrupted then it is skipped.

Trait Implementations

It doesn’t require to implement MaxEncodedLen and give no information for max_size.

Build into entries the storage metadata entries of a storage given some docs.

Module prefix. Used for generating final key.

Storage prefix. Used for generating final key.

Final full prefix that prefixes all keys.

Remove all value of the storage.

Iter over all value of the storage. Read more

Translate the values of all elements by a function f, in the map in no particular order. By returning None from f for an element, you’ll remove it from the map. Read more

Auto Trait Implementations

Blanket Implementations

Gets the TypeId of self. Read more

Immutably borrows from an owned value. Read more

Mutably borrows from an owned value. Read more

Convert from a value of T into an equivalent instance of Option<Self>. Read more

Consume self to return Some equivalent value of Option<T>. Read more

Convert Box<dyn Trait> (where Trait: Downcast) to Box<dyn Any>. Box<dyn Any> can then be further downcast into Box<ConcreteType> where ConcreteType implements Trait. Read more

Convert Rc<Trait> (where Trait: Downcast) to Rc<Any>. Rc<Any> can then be further downcast into Rc<ConcreteType> where ConcreteType implements Trait. Read more

Convert &Trait (where Trait: Downcast) to &Any. This is needed since Rust cannot generate &Any’s vtable from &Trait’s. Read more

Convert &mut Trait (where Trait: Downcast) to &Any. This is needed since Rust cannot generate &mut Any’s vtable from &mut Trait’s. Read more

Convert Arc<Trait> (where Trait: Downcast) to Arc<Any>. Arc<Any> can then be further downcast into Arc<ConcreteType> where ConcreteType implements Trait. Read more

Performs the conversion.

Instruments this type with the provided Span, returning an Instrumented wrapper. Read more

Instruments this type with the current Span, returning an Instrumented wrapper. Read more

Performs the conversion.

Get a reference to the inner from the outer.

Get a mutable reference to the inner from the outer.

Should always be Self

Convert from a value of T into an equivalent instance of Self. Read more

Consume self to return an equivalent value of T. Read more

The type that get/take return.

Get the storage key used to fetch a value corresponding to a specific key.

Swap the values of two keys.

Does the value (explicitly) exist in storage?

Load the value associated with the given key from the map.

Try to get the value for the given key from the map. Read more

Store a value to be associated with the given key from the map.

Remove the value under a key.

Mutate the value under a key.

Mutate the value under a key. Read more

Mutate the item, only if an Ok value is returned.

Mutate the item, only if an Ok value is returned. Deletes the item if mutated to a None.

Take the value under a key.

Append the given items to the value in the storage. Read more

Migrate an item with the given key from a defunct OldHasher to the current hasher. Read more

Read the length of the storage value without decoding the entire value under the given key. Read more

Migrate an item with the given key from a blake2_256 hasher to the current hasher. Read more

Try and append the item into the storage map at the given key. Read more

The type returned in the event of a conversion error.

Performs the conversion.

The type returned in the event of a conversion error.

Performs the conversion.

The counterpart to unchecked_from.

Consume self to return an equivalent value of T.

Attaches the provided Subscriber to this type, returning a WithDispatch wrapper. Read more

Attaches the current default Subscriber to this type, returning a WithDispatch wrapper. Read more