Passing Parameters to Builtin Studies

[Book]

The examples I have seen so far create builtin study objects outside of main(). This seems reasonable since creating an object on every tick (or bar with setComputeOnClose) would likely impose a heavy processor load.

However, the only method I have seen to pass user-configurable parameters to efs code, such as specifying the length of a moving average, is through arguments to main(). But if a study object is created before main(), it appears you cannot set its parameters that way.

Is there another way of passing parameters to a formula, or is there a method to alter a study object's parameters after it's created? Or is there any other way to code using builtin studies that allows the user to affect its paramters?

[eSignal_JasonK]

Hello Book,

You can pass input parameters to a built-in study and allow the object to only be created once by checking for a bar state of BARSTATE_ALLBARS. Download PassInputsToStudy.efs to see an example using MAStudy.

[Book]

Good idea. The following seems to work. Note you need to declare the variable globally, outside of main, but you can create the object inside BARSTATE_ALLBARS:

function premain() { ... }
var study;
function main(MAlen) {
if (MAlength == null) MAlen = 10;
if(getBarState() == BARSTATE_ALLBARS) {
study = new MAStudy(MAlen, 0, "Close", MAStudy.SIMPLE);
}
...
}

[I wish they would let us tabify code.]

Thanks,
Book

[eSignal_JasonK]

Hi Book,

I agree. It would be nice if we could use tab when writing replies to posts. It's a problem with HTML syntax. In a web page, tab is used to move from object to object. Anyway, to get around this, I write the code in Notepad or the EFS editor in eSignal and then just copy it into the text box when posting replies. You can also surround the code with [php ] [/php ] and it will colorize it. Note: you'll have to take out the space before the end brackets for it to work. Try it out on your next post.

function preMain() {
    setPriceStudy(true);
}

function main() {
    // code;
} 

[mattgundersen]

FYI - I'd recommend it be done this way. Checking to see if the study is null rather than ALLBARS

function premain() { ... }

var study = null;

function main(MAlen) {
    if (MAlength == null) MAlen = 10;

    if(study == null)
        study = new MAStudy(MAlen, 0, "Close", MAStudy.SIMPLE);

    ...
}