Sax.Handler behaviour (sax v1.0.0) View Source
This module provides callbacks to implement SAX events handler.
Link to this section Summary
Callbacks
Callback for event handling.
Link to this section Types
Specs
characters_data() :: String.t()
Specs
end_document_data() :: any()
Specs
end_element_data() :: name :: String.t()
Specs
event_data() :: start_element_data() | end_document_data() | start_element_data() | end_element_data() | characters_data()
Specs
event_name() :: :start_document | :end_document | :start_element | :characters | :end_element
Specs
start_document_data() :: Keyword.t()
Specs
Link to this section Callbacks
Specs
handle_event( event_type :: event_name(), data :: event_data(), user_state :: any() ) :: {:ok, user_state :: any()} | {:stop, returning :: any()}
Callback for event handling.
This callback takes an event type, an event data and user_state
as the input.
The initial user_state
is the third argument in Sax.parse_string/3
and Sax.parse_stream/3
.
It can be accumulated and passed around during the parsing time by returning it as the result of
the callback implementation, which can be used to keep track of data when parsing is happening.
Returning {:ok, new_state}
continues the parsing process with the new state.
Returning {:stop, anything}
stops the prosing process immediately, and anything
will be returned.
This feature is usually handy when we want to get the desired return without parsing the whole file.
SAX Events
There are a couple of events that need to be handled in the handler.
:start_document
.:start_element
.:characters
–the binary that matchesCharData*
and Reference. Note that it is not trimmed and includes ALL whitespace characters that matchCharData
.:end_document
.:end_element
.
Check out event_data()
type for more information of what are emitted for each event type.
Examples
defmodule MyEventHandler do
@behaviour Sax.Handler
def handle_event(:start_document, prolog, state) do
{:ok, [{:start_document, prolog} | state]}
end
def handle_event(:end_document, _data, state) do
{:ok, [{:end_document} | state]}
end
def handle_event(:start_element, {name, attributes}, state) do
{:ok, [{:start_element, name, attributes} | state]}
end
def handle_event(:end_element, name, state) do
{:ok, [{:end_element, name} | state]}
end
def handle_event(:characters, chars, state) do
{:ok, [{:chacters, chars} | state]}
end
end