coldfusion IIF error - Invalid CFML construct found

I am getting an an error "Invalid CFML construct found"

iif(stImages[id][1]["seolink"] is not "", 开发者_JAVA百科stImages[id][1]["seolink"], stImages[id][1]["url"]) />

what i am doing here wrong?

Try:

iif(stImages[id][1]["seolink"] is not "", DE(stImages[id][1]["seolink"]), DE(stImages[id][1]["url"])) />

For those readers playing from home (as it were), IIF can be an unruly beast because of the double evaluation it does. So

#IIF(myVal EQ "", "thisThing", "thatThing")#

LOOKS like it will simply return the first or second strings, but in fact it will return the content of the VARIABLES "thisThing" or "thatThing" (or throw an error that they don't exist). So say it with me: "IIF() and DE() GO TOGETHER LIKE MUTUALLY BENEFICIAL PARASITIC LIFEFORMS". "DE" as in "Delayed Evaluation". So if you want the above statement to return the first or second string, you need:

#IIF(myVal EQ "", DE("thisThing"), DE("thatThing"))#

Now, you can certainly use this feature to evaluate a field twice and NOT use "DE()", but that means you're using some kind of dynamic variable name, and it could be argued that doing that isn't best practice. Not that I haven't done that exact thing, but it should be copiously commented, because if you don't the person who maintains the code after you will probably want to kill you.

By the way, there's no mystery to "DE()". These two statements are equivalent:

#DE("thisThing")#
#"""thisThing"""#

See what's going on? "DE()" simply puts double quotes around something. So one set of quotes gets "stripped off" the first time it gets evaluated, and then the quoted string gets returned from the function. Clear as mud?

See why people don't like IIF? It's very handy in certain situations, but is a contextual mess and contributes to code that makes people go "HWUUUH??" So that's why people say to avoid it if possible.

I would avoid iif where you can,

iif(stImages[id][1]["seolink"] is not "", DE(stImages[id][1]["seolink"]), DE(stImages[id][1]["url"])) />

<cfif stImages[id][1]["seolink"] is not "">#stImages[id][1]["seolink"]#<cfelse>#stImages[id][1]["url"]#</cfif>

or if you have ColdFusion 9

<cfset stImages[id][1]["seolink"] is not "" ? #stImages[id][1]["seolink"]# : #stImages[id][1]["url"]# />