Keepers

The bank module provides three different exported keeper interfaces which can be passed to other modules which need to read or update account balances. Modules should use the least-permissive interface which provides the functionality they require.

Note that you should always review the bank module code to ensure that permissions are limited in the way that you expect.

Common Types

Input

An input of a multiparty transfer

type Input struct {
  Address AccAddress
  Coins   Coins
}

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Output

An output of a multiparty transfer.

type Output struct {
  Address AccAddress
  Coins   Coins
}

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BaseKeeper

The base keeper provides full-permission access: the ability to arbitrary modify any account's balance and mint or burn coins.

type BaseKeeper interface {
  SetCoins(addr AccAddress, amt Coins)
  SubtractCoins(addr AccAddress, amt Coins)
  AddCoins(addr AccAddress, amt Coins)
  InputOutputCoins(inputs []Input, outputs []Output)
}

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setCoins fetches an account by address, sets the coins on the account, and saves the account.

setCoins(addr AccAddress, amt Coins)
  account = accountKeeper.getAccount(addr)
  if account == nil
    fail with "no account found"
  account.Coins = amt
  accountKeeper.setAccount(account)

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subtractCoins fetches the coins of an account, subtracts the provided amount, and saves the account. This decreases the total supply.

subtractCoins(addr AccAddress, amt Coins)
  oldCoins = getCoins(addr)
  newCoins = oldCoins - amt
  if newCoins < 0
    fail with "cannot end up with negative coins"
  setCoins(addr, newCoins)

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addCoins fetches the coins of an account, adds the provided amount, and saves the account. This increases the total supply.

addCoins(addr AccAddress, amt Coins)
  oldCoins = getCoins(addr)
  newCoins = oldCoins + amt
  setCoins(addr, newCoins)

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inputOutputCoins transfers coins from any number of input accounts to any number of output accounts.

inputOutputCoins(inputs []Input, outputs []Output)
  for input in inputs
    subtractCoins(input.Address, input.Coins)
  for output in outputs
    addCoins(output.Address, output.Coins)

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SendKeeper

The send keeper provides access to account balances and the ability to transfer coins between accounts, but not to alter the total supply (mint or burn coins).

type SendKeeper interface {
  SendCoins(from AccAddress, to AccAddress, amt Coins)
}

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sendCoins transfers coins from one account to another.

sendCoins(from AccAddress, to AccAddress, amt Coins)
  subtractCoins(from, amt)
  addCoins(to, amt)

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ViewKeeper

The view keeper provides read-only access to account balances but no balance alteration functionality. All balance lookups are O(1).

type ViewKeeper interface {
  GetCoins(addr AccAddress) Coins
  HasCoins(addr AccAddress, amt Coins) bool
}

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getCoins returns the coins associated with an account.

getCoins(addr AccAddress)
  account = accountKeeper.getAccount(addr)
  if account == nil
    return Coins{}
  return account.Coins

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hasCoins returns whether or not an account has at least the provided amount of coins.

hasCoins(addr AccAddress, amt Coins)
  account = accountKeeper.getAccount(addr)
  coins = getCoins(addr)
  return coins >= amt

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# Keepers

# Common Types

# Input

# Output

# BaseKeeper

# SendKeeper

# ViewKeeper

Keepers

Common Types

Input

Output

BaseKeeper

SendKeeper

ViewKeeper