Inner Transactions
The following opcodes allow for inner transactions.
Inner transactions allow Applications to have many of the effects of a true top-level transaction, programmatically. However, they are different in significant ways. The most important differences are that:
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They are not signed;
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Duplicates are not rejected;
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They do not appear in the block in the usual way.
Instead, their effects are noted in metadata associated with their top-level application call transaction.
An inner transaction’s sender MUST be the SHA512/256 hash
of the Application ID (prefixed by appID), or an account that has been rekeyed
to that hash.
In Version 5, inner transactions may perform pay, axfer, acfg, and afrz effects.
After executing an inner transaction with itxn_submit, the effects of the transaction
are visible beginning with the next instruction with, for example, balance and
min_balance checks.
In Version 6, inner transactions may also perform keyreg and appl effects. Inner
appl calls fail if they attempt to invoke a program with a Version less than Version
4, or if they attempt to opt-in to an app with a Clear State Program less than Version 4.
In Version 5, only a subset of the transaction’s header fields may be set: Type /
TypeEnum, Sender, and Fee.
In Version 6, header fields Note and RekeyTo may also be set.
For the specific (non-header) fields of each transaction type, any field may be set.
This allows, for example, clawback transactions, asset opt-ins, and asset creates
in addition to the more common uses of axfer and acfg.
All fields default to the zero value, except those described under itxn_begin.
Fields may be set multiple times, but may not be read. The most recent setting is
used when itxn_submit executes. For this purpose Type and TypeEnum are considered
to be the same field. When using itxn_field to set an array field (ApplicationArgs,
Accounts, Assets, or Applications) each use adds an element to the end of
the array, rather than setting the entire array at once.
itxn_field fails immediately for unsupported fields, unsupported transaction types,
or improperly typed values for a particular field. itxn_field makes acceptance
decisions entirely from the field and value provided, never considering previously
set fields.
Illegal interactions between fields, such as setting fields that belong to two different
transaction types, are rejected by itxn_submit.
| OPCODE | DESCRIPTION |
|---|---|
itxn_begin | begin preparation of a new inner transaction in a new transaction group |
itxn_next | begin preparation of a new inner transaction in the same transaction group |
itxn_field f | set field F of the current inner transaction to A |
itxn_submit | execute the current inner transaction group. Fail if executing this group would exceed the inner transaction limit, or if any transaction in the group fails. |
itxn f | field F of the last inner transaction |
itxna f i | Ith value of the array field F of the last inner transaction |
itxnas f | Ath value of the array field F of the last inner transaction |
gitxn t f | field F of the Tth transaction in the last inner group submitted |
gitxna t f i | Ith value of the array field F from the Tth transaction in the last inner group submitted |
gitxnas t f | Ath value of the array field F from the Tth transaction in the last inner group submitted |