Functions returning TRUE or FALSE

Report · Jan 14, 2011

Morning chaps,

Wrote a function that converts a date in the format "01 Jan 2010" to a Unix timestamp. It also returns FALSE if it cannot convert the date it is being passed, which is great because I can use:

<cfif convertDateToUTS(FORM.date)>
     <cfset #date# = #convertDateToUTS(FORM.date)# />
     <p>Your date: <cfoutput>#date#</cfoutput></p>
<cfelse>
     <p>Could not convert date.</p>
</cfif>

Here is the function:

<cffunction name="convertDateToUTS" output="no">
    <cfargument name="date" required="Yes" />
    <cfargument name="time" default="00:00"/>
<cftry>
    <cfset #date# = trim(left(trim(date), 11)) />
    <cfset #time# = trim(left(trim(time), 5)) />
    <cfset #dateArr# = #listToArray(date, " ")# />
    <cfset #dateArr[2]# = #replace(dateArr[2], "Jan", 1)# />
    <cfset #dateArr[2]# = #replace(dateArr[2], "Feb", 2)# />
    ...etc...
    <cfset #dateArr[2]# = #replace(dateArr[2], "Dec", 12)# />
    <cfset #dateTime# = ArrayToList(dateArr, " ")&" "&time />
    <cfset #dateTimeBits# = listToArray(dateTime, " :") />
    <cfset #ODBCdateTime# = CreateODBCDateTime(CreateDateTime(dateTimeBits[3], dateTimeBits[2], dateTimeBits[1], dateTimeBits[4], dateTimeBits[5], 0)) />
    <cfset #unixDateTime# = #DateDiff("s", CreateDate(1970,1,1), ODBCdateTime)# />
    <cfreturn #unixDateTime# />
<cfcatch>
    <cfreturn FALSE />
</cfcatch>
</cftry>
</cffunction>

However, now I want to write a similar one which converts a timestamp to a date in that format:

<cffunction name="convertUTStoDate" output="no">
     <cfargument name="uts" required="Yes" />
<cftry>
     <cfset #date# = #DateFormat(DateAdd("s",uts,"1970/01/01 00:00:00"),"DD MMM YYYY")# />
     <cfset #time# = #TimeFormat(DateAdd("s",uts,"1970/01/01 00:00:00"), "HH:mm")# />
     <cfreturn #date#&" "&#time# />
<cfcatch>
     <cfreturn FALSE />
</cfcatch>
</cftry>
</cffunction>

This does the conversion correctly but it it won't let me use it as the condition in a CFIF like the first function does eg <cfif convertUTStoDate(uts)> but, it does work exactly as I want if I do this: <cfif convertUTStoDate(uts) NEQ FALSE>

What am I doing wrong? I really want it to behave like the first function when used in a condition. Massive thanks to anyone who can help!

T

Report · Jan 14, 2011

I'm surprised the first function worked. Using strings as booleans just seems wrong. I would suggest using an empty string as your return value if the conversion fails and using your if/else logic on the length of the returned value.

Report · Jan 14, 2011

If the input's not valid, it should just raise an appropriate exception. Having a function that might return a date-formatted string, or might return a boolean is just wrong.

--

Adam

Report · Jan 14, 2011

I'm surprised the first function worked. Using strings as
booleans just seems wrong.

It probably worked because the result of the first function is a number and was implicitly treated as boolean.

But I agree that function seems wrong. It is trying to do too much and be all things to all values. If it were me, I would create two functions: one to validate and one to format

ie IsSomeKindOfDate( yourValue )

FormatSomeKindOfDate( yourValue )

Report · Jan 16, 2011

This does the conversion correctly but it it won't let me use it as the condition in a CFIF like the first function does eg <cfif convertUTStoDate(uts)> but, it does work exactly as I want if I do this: <cfif convertUTStoDate(uts) NEQ FALSE>
What am I doing wrong?

The expression <cfif convertUTStoDate(uts)> will only work if ColdFusion can cast convertUTStoDate(uts) to a boolean. That is in turn possible only if that value is a boolean or a number. It fails bacause convertUTStoDate(uts) is a date.

However, the expression <cfif convertUTStoDate(uts) NEQ FALSE> is a comparison. As such, it will always work, so long as convertUTStoDate(uts) is a simple value. It will then be comparing like with like.

Report · Jan 16, 2011

What dou you think of the following version of your code? It is the same as your original code but, in my opinion, a bit simpler. For example, your test now becomes something like

<cfif convertDateToUTS(FORM.date).isConverted>
     <cfset date = convertDateToUTS(FORM.date).unixDateTime/>
     <p>Your date: <cfoutput>#date#</cfoutput></p>
<cfelse>
     <p>Could not convert date.</p>
      Reason: <cfoutput>#convertDateToUTS(FORM.date).message#</cfoutput>
</cfif>

</cftry>
</cffunction>