How to output an array to a comma-deliniated string?

Question

I have an array called device, which looks like this (simplified):

label : "Device 1",
exhibits : [{
    item : 1,
    desc : "This is a sample"
},{
    item : 2,
    desc : "This is another sample"
},{
    item : 3,
    desc : "This is a third"
}]

I'm trying to print exhibits neatly for a PDF, so I'm thinking comma-deliniated like this:

1, 2, 3

This is my code:

<cfloop array="#device.exhibits#" index="exhibit">
    #exhibit.item#
</cfloop>

But I get this:

Yes, I could manually figure out if there should be commas or not, but is there a better way to do this?

You could so some sort of listappend() but that would not get the spaces. — James A Mohler
– James A Mohler, Commented Nov 16, 2018 at 17:53
My compiler sense is tingling: itemNumber is undefined in exhibit. You meant #exhibit.item#, right? :P — Alex
– Alex, Commented Nov 16, 2018 at 23:59

Shawn · Accepted Answer · 2018-11-18 17:28:55Z

3

Since you're using CF11+, you can use the ArrayMap function with an ArrayList to turn the array into a list.

exhibits.map( function(i) { return i.item ; } ).toList() ;

With your example array, it gives you "1,2,3".

In another of my answers, I stepped through handling empty elements. Since this is an array of structs, I don't know if this would be a problem. How are you getting this data for your exhibits array?

EDIT:

exhibits.map( function(i) { return i.item ; } )
    .filter( function(j) { return len(j) ; } )
    .toList() ;

will return the list with empty elements removed.

EDIT 2:

Per the question by @TravisHeeter, if you prefer lambda expressions or arrow functions, you can use them in Lucee 5.

exhibits.map( (i) => i.item ).filter( (j) => len(j) ).toList()

https://trycf.com/gist/907a68127ddb704611b191d494aa94ce/lucee5?theme=monokai

edited Nov 18, 2018 at 17:28

answered Nov 16, 2018 at 19:40

Shawn

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5 Comments

Travis Heeter Over a year ago

I take it CF doesn't have arrow functions yet?

Shawn Over a year ago

@TravisHeeter I don't think Adobe CF does, but Lucee 5 dialect does. See answer update.

Travis Heeter Over a year ago

Unfortunately, I could not get .map nor arrayMap to work, I had to use @Alex's solution.

Shawn Over a year ago

Are you using CF2016? ArrayMap was added back in CF11, so there's no reason it shouldn't work on any modern version of CF. What does your array look like? It may be a referencing problem.

Shawn Over a year ago

trycf.com/gist/549906a224a65edeba15b8a60674ab0e/… << I nested the array like your example, with device being the outer array, and by changing the reference to device.exhibits, it still works. Does your device array have a more complex structure?

Alex · Accepted Answer · 2018-11-17 00:10:33Z

2

The usual approach is to extract the data first:

<!--- extract the itemNumber of every exhibit --->
<cfset itemNumberList = []>
<cfloop array="#device.exhibits#" index="exhibit">
    <cfset itemNumberList.add(exhibit.itemNumber)>
</cfloop>

And then we transform the extracted data to a comma-separated list (string):

<cfset itemNumberList = arrayToList(itemNumberList, ", ")>

<!--- 1, 2, 3 --->
<cfoutput>#itemNumberList#</cfoutput>

Array-mapping (see Shawn's answer) is a more fancy (readable?) way.

answered Nov 17, 2018 at 0:10

Alex

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1 Comment

Shawn Over a year ago

Just realized that .add() falls back into Java. .append() is the CF member function. Personally, I think this integration with parts of Java is one of the very nice things about ColdFusion. I think that Java .add() when building an array is fastest.

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