How to sort an array of structs in ColdFusion

Question

I have an array of structs in ColdFusion. I'd like to sort this array based on one of the attributes in the structs. How can I achieve this? I've found the StructSort function, but it takes a structure and I have an array.

If this is not possible purely in ColdFusion, is it possible in Java somehow (maybe using Arrays.sort(Object[], Comparator))?

Answer 1

Here is something that closely resembles the original StructSort(). It also supports the pathToSubElement argument.

<cffunction name="ArrayOfStructSort" returntype="array" access="public" output="no">
  <cfargument name="base" type="array" required="yes" />
  <cfargument name="sortType" type="string" required="no" default="text" />
  <cfargument name="sortOrder" type="string" required="no" default="ASC" />
  <cfargument name="pathToSubElement" type="string" required="no" default="" />

  <cfset var tmpStruct = StructNew()>
  <cfset var returnVal = ArrayNew(1)>
  <cfset var i = 0>
  <cfset var keys = "">

  <cfloop from="1" to="#ArrayLen(base)#" index="i">
    <cfset tmpStruct[i] = base[i]>
  </cfloop>

  <cfset keys = StructSort(tmpStruct, sortType, sortOrder, pathToSubElement)>

  <cfloop from="1" to="#ArrayLen(keys)#" index="i">
    <cfset returnVal[i] = tmpStruct[keys[i]]>
  </cfloop>

  <cfreturn returnVal>
</cffunction>

Usage / test:

<cfscript> 
  arr = ArrayNew(1);

  for (i = 1; i lte 5; i = i + 1) {
    s = StructNew();
    s.a.b = 6 - i;
    ArrayAppend(arr, s);
  }
</cfscript> 

<cfset sorted = ArrayOfStructSort(arr, "numeric", "asc", "a.b")>

<table><tr>
  <td><cfdump var="#arr#"></td>
  <td><cfdump var="#sorted#"></td>
</tr></table>

Result:

Answer 2

As usual, CFLib.org has exactly what you want.

http://cflib.org/udf/ArrayOfStructsSort

/**
* Sorts an array of structures based on a key in the structures.
*
* @param aofS      Array of structures.
* @param key      Key to sort by.
* @param sortOrder      Order to sort by, asc or desc.
* @param sortType      Text, textnocase, or numeric.
* @param delim      Delimiter used for temporary data storage. Must not exist in data. Defaults to a period.
* @return Returns a sorted array.
* @author Nathan Dintenfass ([email protected])
* @version 1, December 10, 2001
*/
function arrayOfStructsSort(aOfS,key){
        //by default we'll use an ascending sort
        var sortOrder = "asc";        
        //by default, we'll use a textnocase sort
        var sortType = "textnocase";
        //by default, use ascii character 30 as the delim
        var delim = ".";
        //make an array to hold the sort stuff
        var sortArray = arraynew(1);
        //make an array to return
        var returnArray = arraynew(1);
        //grab the number of elements in the array (used in the loops)
        var count = arrayLen(aOfS);
        //make a variable to use in the loop
        var ii = 1;
        //if there is a 3rd argument, set the sortOrder
        if(arraylen(arguments) GT 2)
            sortOrder = arguments[3];
        //if there is a 4th argument, set the sortType
        if(arraylen(arguments) GT 3)
            sortType = arguments[4];
        //if there is a 5th argument, set the delim
        if(arraylen(arguments) GT 4)
            delim = arguments[5];
        //loop over the array of structs, building the sortArray
        for(ii = 1; ii lte count; ii = ii + 1)
            sortArray[ii] = aOfS[ii][key] & delim & ii;
        //now sort the array
        arraySort(sortArray,sortType,sortOrder);
        //now build the return array
        for(ii = 1; ii lte count; ii = ii + 1)
            returnArray[ii] = aOfS[listLast(sortArray[ii],delim)];
        //return the array
        return returnArray;
}

Answer 3

I don't have the reputation points to comment on @mikest34 post above but @russ was correct that this callback no longer works the way it was explained.

It was Adam Cameron who discovered that when using arraySort with a callback, it no longer requires a True/False response but rather:

-1, if first parameter is "smaller" than second parameter
0, if first parameter is equal to second parameter
1, first parameter is "bigger" than second parameter

So the correct callback is:

ArraySort(yourArrayOfStructs, function(a,b) {
    return compare(a.struct_date, b.struct_date);
});

Testing and working in CF2016