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Merge pull request #4225 from ethereum/fixeventtopics

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Clarify events.
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Alex Beregszaszi 2018-06-19 19:00:30 +01:00 committed by GitHub
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1 changed files with 8 additions and 12 deletions
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docs/contracts.rst
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@ -723,22 +723,18 @@ the contract can only see the last 256 block hashes.
Up to three parameters can Up to three parameters can
receive the attribute ``indexed`` which will cause the respective arguments receive the attribute ``indexed`` which will cause the respective arguments
to be searched for: It is possible to filter for specific values of to be stored in a special data structure as so-called "topics", which allows them to be searched for,
indexed arguments in the user interface. for example when filtering a sequence of blocks for certain events. Events can always
be filtered by the address of the contract that emitted the event. Also,
If arrays (including ``string`` and ``bytes``) are used as indexed arguments, the the hash of the signature of the event is one of the topics except if you
Keccak-256 hash of it is stored as topic instead.
The hash of the signature of the event is one of the topics except if you
declared the event with ``anonymous`` specifier. This means that it is declared the event with ``anonymous`` specifier. This means that it is
not possible to filter for specific anonymous events by name. not possible to filter for specific anonymous events by name.
All non-indexed arguments will be stored in the data part of the log. If arrays (including ``string`` and ``bytes``) are used as indexed arguments, the
Keccak-256 hash of it is stored as topic instead. This is because a topic
can only hold a single word (32 bytes).
.. note:: All non-indexed arguments will be :ref:`ABI-encoded <ABI>` into the data part of the log.
Indexed arguments will not be stored themselves. You can only
search for the values, but it is impossible to retrieve the
values themselves.
:: ::