Difference between revisions of "User Defined Function"
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==Overview== | ==Overview== | ||
User defined functions (UDF) are added by NVSE V4. They must be saved as 'object' type scripts that must use the "Function" block type only. Although 'object' type, they must not be attached to any object and are instead called directly by script name from within other scripts, using the [[Call]] command. | User defined functions (UDF) are added by NVSE V4. They must be saved as 'object' type scripts that must use the "Function" block type only. Although 'object' type, they must not be attached to any object and are instead called directly by script name from within other scripts, using the [[Call]] command. | ||
UDFs may optionally return a single value of any type, using the [[SetFunctionValue]] command within them. They may optionally accept | UDFs may optionally return a single value of any type, using the [[SetFunctionValue]] command within them. They may optionally accept up to 15 arguments of any type, which are defined within curly braces: | ||
<pre> | <pre> | ||
scn SomeUDF | |||
int arg1 ; * args are optional | int arg1 ; * args are optional | ||
ref arg2 | ref arg2 | ||
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Begin Function { arg1, arg2, arg3... } | Begin Function { arg1, arg2, arg3... } | ||
; * | ; * do whatever like any other script | ||
End | End | ||
</pre> | </pre> | ||
and called in a similar way to regular functions: | and called in a similar way to regular functions: | ||
<pre> | <pre> | ||
scn SomeOtherScript | |||
... | |||
call SomeUDF arg1, arg2, arg3... | |||
</pre> | |||
let SomeVariable := | However, to assign the return to a variable, [[Let]] must be used rather than <b>set .. to ..</b>, and to use in a conditional, [[Eval|if eval]] rather than simply <b>if</b>: | ||
<pre> | |||
let SomeVariable := call SomeOtherUDF arg1 | |||
if eval (call SomeSuitableUDF) | if eval (call SomeSuitableUDF) | ||
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</pre> | </pre> | ||
== | ==Examples== | ||
<pre> | |||
scn GetRandomForm | |||
; *** This script accepts a form list and returns one random form from it | |||
; local variables | |||
int iCount | |||
int iChoice | |||
ref RandomForm | |||
; arguments | |||
ref rFormList | |||
Begin Function { rFormList } | |||
let iCount := ListGetCount rFormList | |||
let iChoice := Rand 0, iCount | |||
let RandomForm := ListGetNthForm rFormList, iChoice | |||
SetFunctionValue RandomForm | |||
End | |||
</pre> | |||
<pre> | <pre> | ||
scn fnShuffle | scn fnShuffle | ||
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End | End | ||
</pre> | </pre> | ||
==Accepting any type arguments (advanced)== | |||
In some contexts, it is useful to allow arguments of any type for a UDF. Since [[Array Variable|array]] elements can be any type, this can be conveniently achieved using the [[NVSE Expressions]], <b>*</b> ('box') and <b>&</b> ('unbox'), and the [[TypeOf]] / [[GetType]] functions. | |||
<pre> | |||
scn MyUDF | |||
array_var AnyTypeArgument | |||
Begin Function { AnyTypeArgument } | |||
if eval (TypeOf *AnyTypeArgument) == "form" | |||
... | |||
End | |||
</pre> | |||
<pre> | |||
ref MyRef | |||
int MyInt | |||
call MyUDF &MyRef | |||
call MyUDF &MyInt | |||
</pre> | |||
==Notes== | ==Notes== | ||
*UDFs may be used recursively by saving the script once first without the sub call. | *UDFs may be used recursively by saving the script once first without the sub call. | ||
==See Also== | ==See Also== | ||
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*[[Eval]] | *[[Eval]] | ||
*[[Let]] | *[[Let]] | ||
*[[Script Compiler Override]] | |||
==External Links== | ==External Links== | ||
*[ | *[http://www.loverslab.com/topic/26802-tutorial-nvse4-part-2-user-defined-functions-udfs/ Tutorial on User Defined Functions in NVSE 4] | ||
[[Category:NVSE]] | [[Category:NVSE]] | ||
[[Category:User Defined Functions]] | |||