Problems with creating an array of structs

Question

I'm making a blog API and am having some very strange issues when trying to create an array of structs in coldfusion. The top level array will contain the post, as a struct, with a .comments that is an array of all comments under that post, also as structs.

Each of the pieces in the following code work individually. But, somehow when I put them together I end up with an infinitely nested array of structs containing an array of structs etc... all of only the very last element in the top level array of posts.

<cfset posts = VARIABLES.postDao.getBlogPosts(argumentCollection=arguments) />
<cfset result = arraynew(1) />

<cfloop index="i" from="1" to="#arrayLen(posts)#">
  <cfset post = posts[i].getInstance()>
  <cfset StructInsert(post, 'comments', getComments(post.postId))>
  <cfset ArrayAppend(result, post)>
</cfloop>

getBlogPosts returns an array of Post beans.
bean.getInstance() returns a struct with all the data in the bean.
getComments(id) returns an array all comments(structs) for post[id].

Each of these works as intended and is used elsewhere without problems.

The structure of the infinitely nested array is as such:

Array containing Post  
.  Post.comments containing array of comments + Post on end  
.  .  Post.comments containing array of comments + Post on end
.  .  . etc...

I wasn't, but adding variable scoping to the variables fixed it. I honestly don't under stand how that fixed it though. — Phil
– Phil, Commented Nov 15, 2011 at 19:00
When you don't scope, ACF puts each of those in the shared variables scope, so every function in that component is accessing the same variables. So as you loop through calling more functions, your initial variables are being overwritten each time. When you use the var keyword, it puts them into the local scope, and each function has its own local scope that exists only within that function. — Peter Boughton
– Peter Boughton, Commented Nov 15, 2011 at 19:09

Peter Boughton · Accepted Answer · 2011-11-15 18:56:11Z

8

You didn't show the entire code.

I suspect replacing what you did show with either of these will solve the problem:

<cfset local.posts = VARIABLES.postDao.getBlogPosts(argumentCollection=arguments) />
<cfset local.result = arraynew(1) />

<cfloop index="local.i" from="1" to="#arrayLen(local.posts)#">
    <cfset local.post = local.posts[local.i].getInstance()>
    <cfset StructInsert(local.post, 'comments', getComments(local.post.postId))>
    <cfset ArrayAppend(local.result, local.post)>
</cfloop>

Or:

<cfset var posts = VARIABLES.postDao.getBlogPosts(argumentCollection=arguments) />
<cfset var result = arraynew(1) />
<cfset var i = 0 />
<cfset var post = 0 />

<cfloop index="i" from="1" to="#arrayLen(posts)#">
    <cfset post = posts[i].getInstance()>
    <cfset StructInsert(post, 'comments', getComments(post.postId))>
    <cfset ArrayAppend(result, post)>
</cfloop>

You should always use either var keyword or local scope for variables in a cffunction.

You can use VarScoper to check your code for other places where this needs fixing.

answered Nov 15, 2011 at 18:56

Peter Boughton

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1 Comment

Phil Over a year ago

The getComments function used the same result variable to return the array. It was probably this fact that the unscoped variables were causing infinite recursion.

Jake Feasel · Accepted Answer · 2011-11-15 18:53:24Z

0

Please try adding some cfdumps in there and report back what you get:

<cfset posts = VARIABLES.postDao.getBlogPosts(argumentCollection=arguments) />
<cfset result = arraynew(1) />

<cfloop index="i" from="1" to="#arrayLen(posts)#">
  <cfset post = posts[i].getInstance()>
  <cfdump var="#post#">
  <cfset StructInsert(post, 'comments', getComments(post.postId))>
  <cfdump var="#post#">
  <cfset ArrayAppend(result, post)>
  <cfdump var="#result#"><cfabort>
</cfloop>

edit

I think the problem is a child reference to a parent value, which spawns the infinite loop when recursing through the object. Try changing to this:

<cfset posts = VARIABLES.postDao.getBlogPosts(argumentCollection=arguments) />
<cfset result = arraynew(1) />

<cfloop index="i" from="1" to="#arrayLen(posts)#">
  <cfset post = posts[i].getInstance()>
  <cfset StructInsert(post, 'comments', Duplicate(getComments(post.postId)))>
  <cfset ArrayAppend(result, post)>
</cfloop>

edited Nov 15, 2011 at 18:53

answered Nov 15, 2011 at 18:32

Jake Feasel

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5 Comments

Phil Over a year ago

fist post dump: a post struct, second post dump: a post struct + comments that contains an array with 2 comments(structs), result dump: an infinitely nested array->struct.array->struct.... of the first element, because of the abort.

Jake Feasel Over a year ago

Do you still get this infinite recursion behavior when you comment-out the StructInsert(post, 'comments'....) line?

Phil Over a year ago

No, it works fine without that line, but I need to include the comments with the post. A dump of getComments(post.postId) returns an array of comments for each post, like it should.

Jake Feasel Over a year ago

Confirms my suspicion of the problem. Please let me know if the call to Duplicate helps

Phil Over a year ago

Duplicate stopped the infinite recursion, but did not fix the problem. Just had to scope my variables. Thanks for the help.

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