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I would like to test:
<cfif Exists(MyStruct["mittens"])>
</cfif>
If the "mittens" key doesn't exist in MyStruct, what will it return? 0, or ""??
What should replace Exists function?
UPDATE
I tried,
<cfif IsDefined(MyStruct.mittens)>
Which also throws the error
Element Mittens is undefined in MyStruct.
705
ColdFusion structures consist of key-value pairs. Structures let you build a collection of related variables that are grouped under a single name. You can define ColdFusion structures dynamically. You can use structures to reference related values as a unit, rather than individually.
Tests for a parameter's existence, tests its data type, and, if. a default value is not assigned, optionally provides one.
Use the isNull() method to evaluate for nothingness and use the null keyword to create a null value (ACF 2018+, Lucee 4.1+). In previous versions, use the function call javaCast( "null", "" ) for ACF or in Lucee you can use the nullValue() function. Take note that in Adobe CF 2018+ you must enable the setting.
To test for key existence, I recommend:
<cfif StructKeyExists(MyStruct, "mittens")>
<!--- or --->
<cfset key = "mittens">
<cfif StructKeyExists(MyStruct, key)>
Behind the scenes this calls the containsKey() method of the java.util.map the ColdFusion struct is based on. This is arguably the fastest method of finding out if a key exists.
The alternative is:
<cfif IsDefined("MyStruct.mittens")>
<!--- or --->
<cfset key = "mittens">
<cfif IsDefined("MyStruct.#key#")>
Behind the scenes this calls Eval() on the passed string (or so I believe) and tells you if the result is a variable reference. In comparison this is slower than StructKeyExists(). On the plus side: You can test for a sub-key in a nested structure in one call:
<cfif IsDefined("MyStruct.with.some.deeply.nested.key")>
Found the answer here
It's StructKeyExists
40
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