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How to I evaluate a query and store one of the resulting entities?

tim268tim268 Member, Developers Posts: 3 PRO
edited October 2017 in FeatureScript
Hello,

I am hoping you can help me.

I would like to find the 2 largest Cylindrical surfaces on a part by surface area.

I can do this, but I think there must be a better method? I am used to object oriented programming in java where I could store this sort of thing using an object.

I havn't put the full code (as it long and may confuse things) but the basic method I am using at the moment:


// Query the all cylindrical faces
var cyls = qGeometry(qOwnedByBody(part, EntityType.FACE), GeometryType.CYLINDER);

var counter = 0;
var cylOneIndex = 0;
var cylTwoIndex = 0;

// Loop through the cylindrical faces
for (var cyl in evaluateQuery(context, cyls))
{

                var cylArea = evArea(context, {
                        "entities" : cyl
                    });

                // If the surface is largest by area - store it's array position/index
                cylOneIndex = counter;

                // If the surface is second largest by area  - store it's array position/index
                cylTwoIndex = counter;

counter += 1;

}


Then, if I want to use either of the 2 largest surfaces later on, I use Query Nth element (because I now know the  position/index):

qNthElement(cyls, cylOneIndex);

or

qNthElement(cyls, cylTwoIndex);


Is there a better way of doing this? Is it possible to evaluate a query and store one of the resulting entities? For example:


// Query the all cylindrical faces
var cyls = qGeometry(qOwnedByBody(part, EntityType.FACE), GeometryType.CYLINDER);

// Initialise the Cylinders as undefined??
var cylOne is Cylinder = undefined;
var cylTwo is Cylinder = undefined;

// Loop through the cylindrical faces
for (var cyl in evaluateQuery(context, cyls))
{

                var cylArea = evArea(context, {
                        "entities" : cyl
                    });

                // If the surface is largest by area - store the Cylinder
                cylOne = cyl;

                // If the surface is second largest by area  - store the Cylinder
                cylTwo = cyl;

}

Then, if I want to use either of the 2 largest surfaces later on, I just used the cylOne or cylTwo variables? For example:

cylOne.radius;

or

cylTwo.radius;


My concerns with my current method are:
  • I am evaluating the query twice. I assume this is poor on performance?
  • What if the index/position of the entities changes in the array?
  • There must be a better way of doing this?

Any help would be appreciated! Thank you

Tim


Comments

  • konstantin_shiriazdanovkonstantin_shiriazdanov Member Posts: 908 ✭✭✭✭✭
    after you got the query of cylindrical faces by
    var cyls = qGeometry(qOwnedByBody(part, EntityType.FACE), GeometryType.CYLINDER);
    i would reccomend to make a list of map structures for each face like {"query": cylFaceQuery,"area":cylFaceArea}
    and sort that list with sort() function. the compare function should be: function(cyl1, cyl2) {return cyl2.area-cyl1.area}
    the two first elements of resulting list will contain the query and the area of two largest by area cylinders
  • tim268tim268 Member, Developers Posts: 3 PRO
    Hello Konstantin,

    Thank you for your quick response.

    Would you be able to explain how I make a list of map structures?
    Do I define an empty var? Loop through and add the maps to the var?

    // Query the all cylindrical faces
    var cyls = qGeometry(qOwnedByBody(part, EntityType.FACE), GeometryType.CYLINDER);

    //Define Empty var?
    var cylList;

    // Loop through the cylindrical faces
    for (var cyl in evaluateQuery(context, cyls))
    {

                    var cylArea = evArea(context, {
                            "entities" : cyl
                        });

                    // Add a map to the array??
                    cylList + {"query": cyl,"area":cylArea};

    }

    sort(cylList ,function(cyl1, cyl2) {return cyl2.area-cyl1.area;});


    I will try and work this out. But again any help would be appreciated. Thank you!

    Tim








  • konstantin_shiriazdanovkonstantin_shiriazdanov Member Posts: 908 ✭✭✭✭✭
    edited October 2017
    something like this - define an empty list and append it with newly calculated values in the loop

    var cylList=[];

    // Loop through the cylindrical faces
    for (var cyl in evaluateQuery(context, cyls))
    {
                    var cylArea = evArea(context, { "entities" : cyl });

                    cylList = append(cylList, {"query": cyl,"area":cylArea});
    }
  • tim268tim268 Member, Developers Posts: 3 PRO
    Got it!

    Thank you so much. I couldn't work out how to init an empty array and then append to it!

    I've been trying:

    var cylList = null;
    var cylList = undefined;
    var cylList[5];
    etc. etc.

    And:

    cylList[counter] = {"query": cyl,"area":cylArea};
    cylList += {"query": cyl,"area":cylArea};
    cylList.set(counter) = {"query": cyl,"area":cylArea};
    etc. etc.


    Seems stupid when you know  how!

    Thank you very much.

    Tim



  • konstantin_shiriazdanovkonstantin_shiriazdanov Member Posts: 908 ✭✭✭✭✭
    yep, featurescript doesn't pamper us by too big amount of syntax sugar :) so if you going to perform some standart operation to data structure you should likely search a function for this in its standart library
  • ilya_baranilya_baran Onshape Employees, Developers, HDM Posts: 928
    There are qLargest and qSmallest queries that you can use for this.  To get the second largest face, you can do something like:
    var largestQuery = qLargest(faces);
    var secondLargest = qLargest(qSubtraction(faces, largestQuery));
    Ilya Baran \ Director, Architecture and FeatureScript \ Onshape Inc
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