Loop over array of structures and output specific struct value?

Question

I have array of structures where I should access specific field. Here is example of my data:

array
1   
   struct
   address_city     Washington
   address_state    DC
array
2   
   struct
   address_city     New York
   address_state    NY
array
3   
   struct
   address_city     Miami
   address_state    FL

I have this code to loop over array and then inner loop to iterate over structures:

<cfloop from="1" to="#arrayLen(arrData)#" index="i">
    <cfset data = arrData[i]>
    <cfloop collection="#data#" item="key">
        <cfoutput>#key#:#data[key]#<br></cfoutput>
    </cfloop> 
</cfloop>

Code above will produce this output:

address_city:Washington
address_state:DC
address_city:New York
address_state:NY
address_city:Miami
address_state:FL

Instead I need to access only address_state value. I have tried something like this:

<cfloop from="1" to="#arrayLen(arrData)#" index="i">
    <cfset data = arrData[i]>
    <cfloop collection="#data#" item="key">
        <cfoutput>#data[key]['address_state']#<br></cfoutput>
    </cfloop> 
</cfloop>

Then I was getting this error message:

Message     You have attempted to dereference a scalar variable of type class java.lang.String as a structure with members.

Is there a way to output only one field from each structure in array? Something similar is doable in JavaScript when iterating over JS Object. Example:

for (var key in data) {
    console.log(data[key]['address_state']);
}

If anyone knows the way to achieve this in ColdFusion please let me know.

@CFML_Developer Have you tried that code? It's not correct output. It will do this: DC DC NY NY FL FL It will output state value for each item in the structure. — espresso_coffee
– espresso_coffee, Commented Dec 4, 2018 at 18:41
Perhaps the downvoter can explain the downvote. I see nothing wrong with this question. — Dan Bracuk
– Dan Bracuk, Commented Dec 4, 2018 at 21:50

Shawn · Accepted Answer · 2018-12-04 18:40:45Z

3

Funny enough, there is a way to do it almost exactly like the JS example.

for (key in data) {
    writeOutput( "Address State = " & key.address_state & "<br>");
}

https://trycf.com/gist/f0bd28bbf644912d320b10fdc5f526f4/acf?theme=monokai

You were getting the error because you were referencing the data array when you didn't need to. You were already looping through the keys in data by nature of your loop. In your script example, you didn't need to do a double loop through your array.

edited Dec 4, 2018 at 18:40

answered Dec 4, 2018 at 18:37

Shawn

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10 Comments

espresso_coffee Over a year ago

I use ColdFusion 10 not sure that is supported. At least when I tried I got the same error that I mentioned above.

Shawn Over a year ago

Adobe CF10? That TryCF.com link is in ColdFusion 10. It should work. Did you try the exact code sample I included? It shouldn't give you an error like that.

Shawn Over a year ago

@espresso_coffee Can you use TryCF to create your data structure? Is it a single array that holds structs of data? Or is it an array that holds other arrays that hold struct data?

espresso_coffee Over a year ago

IT WORKS! Funny enough only when I use cfscript, If I try to do that with cfml then I get the error.

Shawn Over a year ago

@espresso_coffee You shouldn't loop over a query. That will cause a lot of unnecessary network activity, and reconnecting each loop will cause a significant amount of latency. You'd be better to write a query that can get multiple results or perform multiple inserts in one call. What database are you using?

|

AishuSuhan P · Accepted Answer · 2018-12-05 10:27:39Z

2

I've go through your issue and I hope you got a answer based on script based coding style. But As you said in above comments you need functionality based on tag. So here I've post my functionality based on tag. I hope it's will help you. Thanks.

<cfloop array ="#arrData#" index="data">
    Address_State: #data.address_state# <br>
</cfloop>

answered Dec 5, 2018 at 10:27

AishuSuhan P

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2 Comments

Shawn Over a year ago

Just a note, but I don't see where OP said he had to use tags. Regardless, even though it's CF10, I'd still recommending using script anywhere that it's possible (which is close to everything in 10). I think the tagginess of CF is one of the reasons it gets bashed (though it also can make it easy to learn/use). But pointing out that an array loop is much more appropriate is a big key here.

Dawesi Over a year ago

Agree, this is THE correct answer to the question.

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