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authorRaimo Niskanen <[email protected]>2016-02-24 16:36:24 +0100
committerRaimo Niskanen <[email protected]>2016-02-24 16:36:24 +0100
commit14028aee428c135211e33df77c1bee2fdc128f6e (patch)
treef5788ddaa552b89b661cfaec8530e927b7efcb89 /lib/stdlib/doc/src
parent8b16506b0763d13b69aef3baeabef4729c708fe5 (diff)
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Ditch PrevState
StateName/4 -> StateName/3 handle_event/5 -> handle_event/4
Diffstat (limited to 'lib/stdlib/doc/src')
-rw-r--r--lib/stdlib/doc/src/gen_statem.xml70
1 files changed, 24 insertions, 46 deletions
diff --git a/lib/stdlib/doc/src/gen_statem.xml b/lib/stdlib/doc/src/gen_statem.xml
index 1e41d616e9..f21610d14c 100644
--- a/lib/stdlib/doc/src/gen_statem.xml
+++ b/lib/stdlib/doc/src/gen_statem.xml
@@ -62,12 +62,12 @@ gen_statem:stop -----> Module:terminate/2
gen_statem:call
gen_statem:cast
erlang:send
-erlang:'!' -----> Module:StateName/4
- Module:handle_event/5
+erlang:'!' -----> Module:StateName/3
+ Module:handle_event/4
- -----> Module:terminate/3
-- -----> Module:code_change/3</pre>
+- -----> Module:code_change/4</pre>
<p>Events are of different
<seealso marker="#type-event_type">types</seealso>
so the callback functions can know the origin of an event
@@ -91,28 +91,22 @@ erlang:'!' -----> Module:StateName/4
is <c>state_functions</c> the state has to be an atom and
is used as the state function name.
See
- <seealso marker="#Module:StateName/4">
- <c>Module:StateName/4</c>
+ <seealso marker="#Module:StateName/3">
+ <c>Module:StateName/3</c>
</seealso>.
This gathers all code for a specific state
in one function and hence dispatches on state first.
Note that in this mode the callback function
- <seealso marker="#Module:code_change/4">
- <c>Module:code_change/4</c>
- </seealso> makes the state name <c>code_change</c>
- unusable. Actually you might get away with using it
- as a state name but you will have to find a way to separate
- the two callback roles e.g by observing that you can force
- argument 3 into having different types for the different roles.
- This is a slippery slope, though. It is easier
- to simply not use <c>code_change</c> as a state name.
+ <seealso marker="#Module:terminate/3">
+ <c>Module:terminate/3</c>
+ </seealso> makes the state name <c>terminate</c> unusable.
</p>
<p>When
<seealso marker="#type-callback_mode">callback_mode</seealso>
is <c>handle_event_function</c> the state can be any term
and the state function name is
- <seealso marker="#Module:handle_event/5">
- <c>Module:handle_event/5</c>
+ <seealso marker="#Module:handle_event/4">
+ <c>Module:handle_event/4</c>
</seealso>.
This makes it easy to dispatch on state or on event as
you like but you will have to implement it.
@@ -120,12 +114,6 @@ erlang:'!' -----> Module:StateName/4
states so you do not accidentally postpone one event
forever creating an infinite busy loop.
</p>
- <p>There is a small gotcha in both callback modes regarding
- the state <c>undefined</c> that is used as the previous state
- when the first state function is called. So either do not
- use <c>undefined</c> as a state, or figure out
- the implications yourself.
- </p>
<p>The <c>gen_statem</c> enqueues incoming events in order of arrival
and presents these to the
<seealso marker="#state_function">state function</seealso>
@@ -378,14 +366,14 @@ erlang:'!' -----> Module:StateName/4
<item>The state has to be of type
<seealso marker="#type-state_name"><c>state_name()</c></seealso>
and one callback function per state that is
- <seealso marker="#Module:StateName/4">
- <c>Module:StateName/4</c>
- </seealso> is used. This is the default.
+ <seealso marker="#Module:StateName/3">
+ <c>Module:StateName/3</c>
+ </seealso> is used.
</item>
<tag><c>handle_event_function</c></tag>
<item>The state can be any term and the callback function
- <seealso marker="#Module:handle_event/5">
- <c>Module:handle_event/5</c>
+ <seealso marker="#Module:handle_event/4">
+ <c>Module:handle_event/4</c>
</seealso> is used for all states.
</item>
</taglist>
@@ -1054,9 +1042,10 @@ erlang:'!' -----> Module:StateName/4
<c>CallbackMode</c> selects the
<seealso marker="#type-callback_mode">callback_mode()</seealso>.
of the <c>gen_statem</c>.
- <c>State</c> is the <seealso marker="#type-state">state()</seealso>
- of the <c>gen_statem</c> and
- <c>Data</c> the server <seealso marker="#type-data">data()</seealso>
+ <c>State</c> is the initial
+ <seealso marker="#type-state">state()</seealso>
+ and <c>Data</c> the initial server
+ <seealso marker="#type-data">data()</seealso>
</p>
<p>The <seealso marker="#type-action"><c>Actions</c></seealso>
are executed when entering the first
@@ -1076,11 +1065,10 @@ erlang:'!' -----> Module:StateName/4
</func>
<func>
- <name>Module:StateName(EventType, EventContent,
- PrevStateName, Data) -> Result
+ <name>Module:StateName(EventType, EventContent, Data) -> Result
</name>
<name>Module:handle_event(EventType, EventContent,
- PrevState, State, Data) -> Result
+ State, Data) -> Result
</name>
<fsummary>Handle an event</fsummary>
<type>
@@ -1088,10 +1076,7 @@ erlang:'!' -----> Module:StateName/4
<seealso marker="#type-event_type">event_type()</seealso>
</v>
<v>EventContent = term()</v>
- <v>PrevStateName =
- <seealso marker="#type-state_name">state_name()</seealso>
- </v>
- <v>PrevState = State =
+ <v>State = NewState =
<seealso marker="#type-state">state()</seealso>
</v>
<v>Data = NewData =
@@ -1109,9 +1094,9 @@ erlang:'!' -----> Module:StateName/4
<seealso marker="#cast/2">cast/2</seealso> or
as a normal process message one of these functions is called.
If <seealso marker="#type-callback_mode">callback_mode</seealso>
- is <c>state_functions</c> then <c>Module:StateName/4</c> is called,
+ is <c>state_functions</c> then <c>Module:StateName/3</c> is called,
and if it is <c>handle_event_function</c>
- then <c>Module:handle_event/5</c> is called.
+ then <c>Module:handle_event/4</c> is called.
</p>
<p>If <c>EventType</c> is
<seealso marker="#type-event_type"><c>{call,Caller}</c></seealso>
@@ -1126,13 +1111,6 @@ erlang:'!' -----> Module:StateName/4
<c>reply(Caller, Reply)</c>
</seealso>.
</p>
- <p><c>PrevStateName</c> and <c>PrevState</c> are useful
- in some odd cases for example when you want to do something
- only at the first event in a state, or when you need to
- handle events differently depending on the previous state.
- Note that when <c>gen_statem</c> enters its first state
- this is set to <c>undefined</c>.
- </p>
<p>If this function returns with a new state that
does not match equal (<c>=/=</c>) to the current state
all postponed events will be retried in the new state.