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< section class = "tex2jax_ignore mathjax_ignore" id = "return-custom-errors-on-missing-exits" >
< h1 > Return custom errors on missing Exits< a class = "headerlink" href = "#return-custom-errors-on-missing-exits" title = "Permalink to this headline" > ¶< / a > < / h1 >
< div class = "highlight-none notranslate" > < div class = "highlight" > < pre > < span > < / span > > north
Ouch! You bump into a wall!
> out
But you are already outside ...?
< / pre > < / div >
< / div >
< p > Evennia allows for exits to have any name. The command “kitchen” is a valid exit name as well as “jump out the window” or “north”. An exit actually consists of two parts: an < a class = "reference internal" href = "../Components/Objects.html" > < span class = "doc std std-doc" > Exit Object< / span > < / a > and
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an < a class = "reference internal" href = "../Components/Commands.html" > < span class = "doc std std-doc" > Exit Command< / span > < / a > stored on said exit object. The command has the same key and aliases as the
exit-object, which is why you can see the exit in the room and just write its name to traverse it.< / p >
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< p > So if you try to enter the name of a non-existing exit, Evennia treats is the same way as if you were trying to use a non-existing command:< / p >
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< div class = "highlight-none notranslate" > < div class = "highlight" > < pre > < span > < / span > > jump out the window
Command ' jump out the window' is not available. Type " help" for help.
< / pre > < / div >
< / div >
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< p > Many games don’ ’ < code class = "docutils literal notranslate" > < span class = "pre" > tunnel< / span > < / code > command also offers this functionality). In this case, the error starts to look less logical:< / p >
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< div class = "highlight-none notranslate" > < div class = "highlight" > < pre > < span > < / span > > west
Command ' west' is not available. Maybe you meant " set" or " reset" ?
< / pre > < / div >
< / div >
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< p > Since we for our particular game < em > know< / em > that west is an exit direction, it would be better if the error message just told us that we couldn’ < / p >
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< div class = "highlight-none notranslate" > < div class = "highlight" > < pre > < span > < / span > > west
You cannot move west.
< / pre > < / div >
< / div >
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< p > The way to do this is to give Evennia an < em > alternative< / em > Command to use when no Exit-Command is found in the room. See < a class = "reference internal" href = "Beginner-Tutorial/Part1/Beginner-Tutorial-Adding-Commands.html" > < span class = "doc std std-doc" > Adding Commands< / span > < / a > for more info about the process of adding new Commands to Evennia.< / p >
< p > In this example we will just echo an error message, but you could do everything (maybe you lose health if you bump into a wall?)< / p >
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< div class = "highlight-python notranslate" > < div class = "highlight" > < pre > < span > < / span > < span class = "c1" > # for example in a file mygame/commands/movecommands.py< / span >
< span class = "kn" > from< / span > < span class = "nn" > evennia< / span > < span class = "kn" > import< / span > < span class = "n" > default_cmds< / span > < span class = "p" > ,< / span > < span class = "n" > CmdSet< / span >
< span class = "k" > class< / span > < span class = "nc" > CmdExitError< / span > < span class = "p" > (< / span > < span class = "n" > default_cmds< / span > < span class = "o" > .< / span > < span class = "n" > MuxCommand< / span > < span class = "p" > ):< / span >
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< span class = "w" > < / span > < span class = "sd" > " " " Parent class for all exit-errors." " " < / span >
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< span class = "n" > locks< / span > < span class = "o" > =< / span > < span class = "s2" > " cmd:all()" < / span >
< span class = "n" > arg_regex< / span > < span class = "o" > =< / span > < span class = "sa" > r< / span > < span class = "s2" > " \s|$" < / span >
< span class = "n" > auto_help< / span > < span class = "o" > =< / span > < span class = "kc" > False< / span >
< span class = "k" > def< / span > < span class = "nf" > func< / span > < span class = "p" > (< / span > < span class = "bp" > self< / span > < span class = "p" > ):< / span >
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< span class = "w" > < / span > < span class = "sd" > " " " Returns error based on key" " " < / span >
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< span class = "bp" > self< / span > < span class = "o" > .< / span > < span class = "n" > caller< / span > < span class = "o" > .< / span > < span class = "n" > msg< / span > < span class = "p" > (< / span > < span class = "sa" > f< / span > < span class = "s2" > " You cannot move < / span > < span class = "si" > {< / span > < span class = "bp" > self< / span > < span class = "o" > .< / span > < span class = "n" > key< / span > < span class = "si" > }< / span > < span class = "s2" > ." < / span > < span class = "p" > )< / span >
< span class = "k" > class< / span > < span class = "nc" > CmdExitErrorNorth< / span > < span class = "p" > (< / span > < span class = "n" > CmdExitError< / span > < span class = "p" > ):< / span >
< span class = "n" > key< / span > < span class = "o" > =< / span > < span class = "s2" > " north" < / span >
< span class = "n" > aliases< / span > < span class = "o" > =< / span > < span class = "p" > [< / span > < span class = "s2" > " n" < / span > < span class = "p" > ]< / span >
< span class = "k" > class< / span > < span class = "nc" > CmdExitErrorEast< / span > < span class = "p" > (< / span > < span class = "n" > CmdExitError< / span > < span class = "p" > ):< / span >
< span class = "n" > key< / span > < span class = "o" > =< / span > < span class = "s2" > " east" < / span >
< span class = "n" > aliases< / span > < span class = "o" > =< / span > < span class = "p" > [< / span > < span class = "s2" > " e" < / span > < span class = "p" > ]< / span >
< span class = "k" > class< / span > < span class = "nc" > CmdExitErrorSouth< / span > < span class = "p" > (< / span > < span class = "n" > CmdExitError< / span > < span class = "p" > ):< / span >
< span class = "n" > key< / span > < span class = "o" > =< / span > < span class = "s2" > " south" < / span >
< span class = "n" > aliases< / span > < span class = "o" > =< / span > < span class = "p" > [< / span > < span class = "s2" > " s" < / span > < span class = "p" > ]< / span >
< span class = "k" > class< / span > < span class = "nc" > CmdExitErrorWest< / span > < span class = "p" > (< / span > < span class = "n" > CmdExitError< / span > < span class = "p" > ):< / span >
< span class = "n" > key< / span > < span class = "o" > =< / span > < span class = "s2" > " west" < / span >
< span class = "n" > aliases< / span > < span class = "o" > =< / span > < span class = "p" > [< / span > < span class = "s2" > " w" < / span > < span class = "p" > ]< / span >
< span class = "c1" > # you could add each command on its own to the default cmdset,< / span >
< span class = "c1" > # but putting them all in a cmdset here allows you to< / span >
< span class = "c1" > # just add this and makes it easier to expand with more < / span >
< span class = "c1" > # exit-errors in the future< / span >
< span class = "k" > class< / span > < span class = "nc" > MovementFailCmdSet< / span > < span class = "p" > (< / span > < span class = "n" > CmdSet< / span > < span class = "p" > ):< / span >
< span class = "k" > def< / span > < span class = "nf" > at_cmdset_creation< / span > < span class = "p" > (< / span > < span class = "bp" > self< / span > < span class = "p" > ):< / span >
< span class = "bp" > self< / span > < span class = "o" > .< / span > < span class = "n" > add< / span > < span class = "p" > (< / span > < span class = "n" > CmdExitErrorNorth< / span > < span class = "p" > ())< / span >
< span class = "bp" > self< / span > < span class = "o" > .< / span > < span class = "n" > add< / span > < span class = "p" > (< / span > < span class = "n" > CmdExitErrorEast< / span > < span class = "p" > ())< / span >
< span class = "bp" > self< / span > < span class = "o" > .< / span > < span class = "n" > add< / span > < span class = "p" > (< / span > < span class = "n" > CmdExitErrorWest< / span > < span class = "p" > ())< / span >
< span class = "bp" > self< / span > < span class = "o" > .< / span > < span class = "n" > add< / span > < span class = "p" > (< / span > < span class = "n" > CmdExitErrorSouth< / span > < span class = "p" > ())< / span >
< / pre > < / div >
< / div >
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< p > We pack our commands in a new little cmdset; if we add this to our < code class = "docutils literal notranslate" > < span class = "pre" > CharacterCmdSet< / span > < / code > , we can just add more errors to < code class = "docutils literal notranslate" > < span class = "pre" > MovementFailCmdSet< / span > < / code > later without having to change code in two places.< / p >
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< div class = "highlight-python notranslate" > < div class = "highlight" > < pre > < span > < / span > < span class = "c1" > # in mygame/commands/default_cmdsets.py< / span >
< span class = "kn" > from< / span > < span class = "nn" > commands< / span > < span class = "kn" > import< / span > < span class = "n" > movecommands< / span >
< span class = "c1" > # [...]< / span >
< span class = "k" > class< / span > < span class = "nc" > CharacterCmdSet< / span > < span class = "p" > (< / span > < span class = "n" > default_cmds< / span > < span class = "o" > .< / span > < span class = "n" > CharacterCmdSet< / span > < span class = "p" > ):< / span >
< span class = "c1" > # [...]< / span >
< span class = "k" > def< / span > < span class = "nf" > at_cmdset_creation< / span > < span class = "p" > (< / span > < span class = "bp" > self< / span > < span class = "p" > ):< / span >
< span class = "c1" > # [...]< / span >
< span class = "c1" > # this adds all the commands at once< / span >
< span class = "bp" > self< / span > < span class = "o" > .< / span > < span class = "n" > add< / span > < span class = "p" > (< / span > < span class = "n" > movecommands< / span > < span class = "o" > .< / span > < span class = "n" > MovementFailCmdSet< / span > < span class = "p" > )< / span >
< / pre > < / div >
< / div >
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< p > < code class = "docutils literal notranslate" > < span class = "pre" > reload< / span > < / code > the server. What happens henceforth is that if you are in a room with an Exitobject (let’ ’ < em > overload< / em > your error command (also named “north”). But if you enter a direction without having a matching exit for it, you will fall back to your default error commands:< / p >
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< div class = "highlight-none notranslate" > < div class = "highlight" > < pre > < span > < / span > > east
You cannot move east.
< / pre > < / div >
< / div >
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< p > Further expansions by the exit system (including manipulating the way the Exit command itself is created) can be done by modifying the < a class = "reference internal" href = "../Components/Typeclasses.html" > < span class = "doc std std-doc" > Exit typeclass< / span > < / a > directly.< / p >
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< section id = "why-not-a-single-command" >
< h2 > Why not a single command?< a class = "headerlink" href = "#why-not-a-single-command" title = "Permalink to this headline" > ¶< / a > < / h2 >
< p > So why didn’ < / p >
< div class = "highlight-python notranslate" > < div class = "highlight" > < pre > < span > < / span > < span class = "k" > class< / span > < span class = "nc" > CmdExitError< / span > < span class = "p" > (< / span > < span class = "n" > default_cmds< / span > < span class = "o" > .< / span > < span class = "n" > MuxCommand< / span > < span class = "p" > ):< / span >
< span class = "s2" > " Handles all exit-errors." < / span >
< span class = "n" > key< / span > < span class = "o" > =< / span > < span class = "s2" > " error_cmd" < / span >
< span class = "n" > aliases< / span > < span class = "o" > =< / span > < span class = "p" > [< / span > < span class = "s2" > " north" < / span > < span class = "p" > ,< / span > < span class = "s2" > " n" < / span > < span class = "p" > ,< / span >
< span class = "s2" > " east" < / span > < span class = "p" > ,< / span > < span class = "s2" > " e" < / span > < span class = "p" > ,< / span >
< span class = "s2" > " south" < / span > < span class = "p" > ,< / span > < span class = "s2" > " s" < / span > < span class = "p" > ,< / span >
< span class = "s2" > " west" < / span > < span class = "p" > ,< / span > < span class = "s2" > " w" < / span > < span class = "p" > ]< / span >
< span class = "c1" > #[...]< / span >
< / pre > < / div >
< / div >
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< p > This would < em > not< / em > work the way we want. Understanding why is important.< / p >
< p > Evennia’ < a class = "reference internal" href = "../Components/Commands.html" > < span class = "doc std std-doc" > command system< / span > < / a > compares commands by key and/or aliases. If < em > any< / em > key or alias match, the two commands are considered < em > identical< / em > . When the cmdsets merge, priority will then decide which of these ‘ ’ < / p >
< p > So the above example would work fine as long as there were < em > no Exits at all< / em > in the room. But when we enter a room with an exit “north”, its Exit-command (which has a higher priority) will override the single < code class = "docutils literal notranslate" > < span class = "pre" > CmdExitError< / span > < / code > with its alias ‘ ’ < code class = "docutils literal notranslate" > < span class = "pre" > CmdExitError< / span > < / code > will be gone and while “north” will work, we’ < / p >
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