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Custom language parse, compiler
Hello All,
I have written a small script to automate my and my colleagues usual day to day work, it involves creating keyframes on markers and at specific time.
I was looking at possibility to include a small expression kind of system where I can write small peice of codes to set the keyframe values based on other factors.
Below I have explained my requirement with pseudo code of the script.
function setKeyAt ( property, time, value, expression )
{
var keyIndex = property.addKey( time );
if ( value )
property.setValueAtKey ( keyIndex, val );if ( expression )
{
var val = eval( expression );
property.setValueAtKey ( keyIndex, val );
}
}var prop = PROPERTY_REFERENCE;
var nTime = 1;
var exp = "property.keyValue( keyIndex -2 )";
setKeyAt( prop, nTime, undefined, exp );
above code works for me and creates keys at given time, and assings value which is equal to the value at current index – 2.
I want to extend this and implement a way to incorporate something similar to expressions, so that I can create keys using code
currently what I have is, I am looking for key words in the expression string and then replace those with values based on the current property,
EXAMPLE :
currComp.width
is replaced by evaluated value of below string
var layer = property.propertyGroup( property.propertyDepth );
var comp = layer.containingComp;
comp.width;
Hope I was able to explain my problem, and also hope I am not expecting or attempting too much 😉
Thanks,
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2 Replies
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I’m not sure this is what you’re talking about, but when I need a script to construct an expression where certain elements are not known at the time the script is written, I use an identifiable string like $PARM1, $PARM2, etc. Then I create a function that will substitute the actual string for a placeholder parm at run time.
Dan
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Hello Dan,
I am talking on the similar lines, currently I am also doing pretty much the same way you do, but its really dirty way, and i am still learning the whole coding thing.
currently, I am using a string.contains to find keywords, then using a switch statement I am calculating and substituting the keyswords with calculated values
this works but is surely not the best way to do it. also I want to be able to write keywords for functions for example
/*
Key Object which represents each keyframe in property
*/
function Key ( args )
{}
//This functions takes care of setting the key and assigning the values
Key.prototype.setAt = function ( property, time )
{
var _layer = property.propertyGroup( property.propertyDepth );
var _comp = _layer.containingComp;if ( this.ValueType == undefined || this.ValueType !== property.propertyValueType )
return 0;
if ( this.nTimeOffset == undefined )
return 0;var keyIndex = property.addKey ( time + this.nTimeOffset );
if ( this.nValue !== undefined )
property.setValueAtKey ( keyIndex, this.nValue );if ( this.Expression !== undefined || this.Expression !== "" )
{
var val = eval( this.Expression );
if ( val !== undefined )
property.setValueAtKey ( keyIndex, val );
}
}//helper function which can be called from the script to get the value of certain key frame
function _KeyValueAt ( index )
{}
Sample Expression :
"_keyValueAt ( -2 );"
this expression will be evaluated in the setAt function,this works but I want the function to know the 3 variables
1. property
2. _layer
3. _compso that it can use these to calculate the values
hope I was right to the point this time
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