ComputerCraft Wiki - User contributions [en]

Making an API (tutorial)

2013-10-26T02:37:49Z

ZudoHackz:

== Making an API ==

An API is a program that is not directly executed, but is a collection of variables that can be accessed from any program on that computer.

To make an API, you must create a new file. I will call it ''myapi''. Fill it with variable declarations as normal, but without the ''local'' keyword:

<pre>
-- My awesome new API

myvar = "Hello World!"

function myCoolNewFunction()
print(myvar)
end
</pre>

Now try it out. Save and exit the file, then open the ''lua'' program on your ingame computer. Then type:

<pre>
os.loadAPI("myapi") -- replace myapi with the name of your API.
myapi.myCoolNewFunction()
</pre>

If you have written the program correctly, you will see ''Hello World!'' printed to your screen. Now try:

<pre>
print(myapi.myvar)
</pre>

You should also see ''Hello World!'' printed to your screen. Congratulations, this is your first API!

== Locals vs Globals ==

OK, lets go back to our API.

<pre>
-- My awesome new API

myvar = "Hello World!"

function myCoolNewFunction()
print(myvar)
end
</pre>

If we change our declaration for myvar to local, like this:

<pre>
-- My awesome new API

local myvar = "Hello World!"

function myCoolNewFunction()
print(myvar)
end
</pre>

we should get the same result if we call myCoolNewFunction(). '''REMEMBER: you will need to load the API again to apply your changes!'''

But what happens if you try ''print(myapi.myvar)''?

<pre>

</pre>

It prints nothing. This is because we changed the declaration for myvar to local! This is useful if you want to have a variable visible to only your API. It will also work with functions, like this.

<pre>
-- My awesome new API

local myvar = "Hello World!"

local function myCoolNewFunction()
print(myvar)
end
</pre>

Now if you try to call myCoolNewFunction(), you will get an ''attempt to call nil'' error.

[[Category:Tutorials]]

Making an API (tutorial)

2013-10-26T02:35:26Z

ZudoHackz:

Os.startTimer

2013-09-02T02:34:54Z

ZudoHackz:

{{lowercase}}
{{Function
|name=os.startTimer
|args={{type|number}} time
|api=OS
|returns={{type|number}} timerID
|addon=ComputerCraft
|desc=Adds a timer which will fire a "timer" event once after <var>time</var> seconds have passed. It returns an int which acts as a unique ID for the timer. Fractions of a second are supported, but only down to a game tick, or 1/20 of a second (0.05s). Times are rounded up to the next tick, so os.sleep(1.01) and os.sleep(1.05) both wait for 1.05 seconds.
|examples=
{{Example
|desc=Yields until 3 seconds have passed
|code=os.startTimer(3)<br>os.pullEvent(timer)
}}
}}

[[Category:Lua_Core_Functions]]

Os.startTimer

2013-09-02T02:34:34Z

ZudoHackz:

{{NeedsWork|This page needs an example}}
{{lowercase}}
{{Function
|name=os.startTimer
|args={{type|number}} time
|api=OS
|returns={{type|number}} timerID
|addon=ComputerCraft
|desc=Adds a timer which will fire a "timer" event once after <var>time</var> seconds have passed. It returns an int which acts as a unique ID for the timer. Fractions of a second are supported, but only down to a game tick, or 1/20 of a second (0.05s). Times are rounded up to the next tick, so os.sleep(1.01) and os.sleep(1.05) both wait for 1.05 seconds.
|examples=
{{Example
|desc=Yields until 3 seconds have passed
|code=os.startTimer(3)<br>os.pullEvent(timer)
}}
}}

[[Category:Lua_Core_Functions]]