December 2018
Beginner to intermediate
564 pages
17h 34m
English
Content preview from Blockchain Developer's Guide
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Retrieving and listening to contract events
Now let's look at how to watch for events from a contract. Watching for events is very important because the result of method invocations by transactions are usually returned by triggering events.
Before we get into how to retrieve and watch for events, we need to learn indexed parameters of events. A maximum of three parameters of an event can have the indexed attribute. This attribute is used to signal the node to index it so that the app client can search for events with matching return values. If you don't use the indexed attribute, then it will have to retrieve all the events from the node and filter the ones needed. For example, you can write the logFileAddedStatus event this way:
event logFileAddedStatus(bool ...
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