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firebase::database::ValueListener
This is an abstract class.
#include <listener.h>
Value listener interface.
Summary
Subclasses of this listener class can be used to receive events about data changes at a location. Attach the listener to a location using DatabaseReference::AddValueListener() or Query::AddValueListener(), and OnValueChanged() will be called once immediately, and again when the value changes.
Public functions
|
OnCancelled(const Error & error, const char *error_message)=0
|
virtual void
This method will be triggered in the event that this listener either failed at the server, or is removed as a result of the security and Firebase rules.
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OnValueChanged(const DataSnapshot & snapshot)=0
|
virtual void
This method will be called with a snapshot of the data at this location each time that data changes.
|
Public functions
OnCancelled
virtual void OnCancelled(
const Error & error,
const char *error_message
)=0
This method will be triggered in the event that this listener either failed at the server, or is removed as a result of the security and Firebase rules.
| Details |
| Parameters |
error
|
A code corresponding to the error that occurred.
|
error_message
|
A description of the error that occurred.
|
|
OnValueChanged
virtual void OnValueChanged(
const DataSnapshot & snapshot
)=0
This method will be called with a snapshot of the data at this location each time that data changes.
| Details |
| Parameters |
snapshot
|
The current data at the location.
|
|
~ValueListener
virtual ~ValueListener()
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Last updated 2024-01-23 UTC.
[null,null,["Last updated 2024-01-23 UTC."],[],[],null,["# firebase::database::ValueListener Class Reference\n\nfirebase::database::ValueListener\n=================================\n\n\n**This is an abstract class.**\n\n\n`#include \u003clistener.h\u003e`\n\nValue listener interface.\n\nSummary\n-------\n\nSubclasses of this listener class can be used to receive events about data changes at a location. Attach the listener to a location using [DatabaseReference::AddValueListener()](/docs/reference/cpp/class/firebase/database/query#classfirebase_1_1database_1_1_query_1aeb583c0c607b01692f9aaa9a59432810) or [Query::AddValueListener()](/docs/reference/cpp/class/firebase/database/query#classfirebase_1_1database_1_1_query_1aeb583c0c607b01692f9aaa9a59432810), and [OnValueChanged()](/docs/reference/cpp/class/firebase/database/value-listener#classfirebase_1_1database_1_1_value_listener_1a02ce2f03e20564a124b5d290158494a8) will be called once immediately, and again when the value changes.\n\n| ### Constructors and Destructors ||\n|---|---|\n| [~ValueListener](#classfirebase_1_1database_1_1_value_listener_1ae594401b91d5fcf0020241f8e2a09d3d)`()` ||\n\n| ### Public functions ||\n|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------|\n| [OnCancelled](#classfirebase_1_1database_1_1_value_listener_1a8f97aa3b6378c57d0d4b8cf853a95538)`(const `[Error](/docs/reference/cpp/namespace/firebase/database#namespacefirebase_1_1database_1aacf6e57cd8d76d485eeb3907fc298231)` & error, const char *error_message)=0` | `virtual void` This method will be triggered in the event that this listener either failed at the server, or is removed as a result of the security and Firebase rules. |\n| [OnValueChanged](#classfirebase_1_1database_1_1_value_listener_1a02ce2f03e20564a124b5d290158494a8)`(const `[DataSnapshot](/docs/reference/cpp/class/firebase/database/data-snapshot#classfirebase_1_1database_1_1_data_snapshot)` & snapshot)=0` | `virtual void` This method will be called with a snapshot of the data at this location each time that data changes. |\n\nPublic functions\n----------------\n\n### OnCancelled\n\n```c++\nvirtual void OnCancelled(\n const Error & error,\n const char *error_message\n)=0\n``` \nThis method will be triggered in the event that this listener either failed at the server, or is removed as a result of the security and Firebase rules.\n\n\u003cbr /\u003e\n\n| Details ||\n|------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|\n| Parameters | |-----------------|--------------------------------------------------| | `error` | A code corresponding to the error that occurred. | | `error_message` | A description of the error that occurred. | |\n\n### OnValueChanged\n\n```c++\nvirtual void OnValueChanged(\n const DataSnapshot & snapshot\n)=0\n``` \nThis method will be called with a snapshot of the data at this location each time that data changes.\n\n\u003cbr /\u003e\n\n| Details ||\n|------------|-------------------------------------------------------------------------------------------------------|\n| Parameters | |------------|-----------------------------------| | `snapshot` | The current data at the location. | |\n\n### \\~ValueListener\n\n```c++\nvirtual ~ValueListener()\n```"]]
