· Jun 1, 2016

What is the best way to serialize object/list/array/etc to string?


Are there any short ways of serializing COS entity to the string? I am searching for something like .$toJSON() , but I need Caché 2013.* support.

The one way I supposed to work is to use $listbuild:


set str = $LISTTOSTRING($LB(1,2,3,",",5))
set list = $LISTFROMSTRING(str,",")
zw list


But the problem is that $listbuild does not escape delimiters, and it is not possible to deserialize serialized string. The structure I need to serialize may contain any characters.

Are there any short ways to do this in Caché to avoid writing custom parser?

Discussion (15)2
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Now it becomes clear!

I had wondered if your requirement for "string" was that it contained only printable characters. In such a case one solution could be to base64-encode the result of $listbuild. On a Unicode instance of Caché you'd need to convert it to UTF8 first.

USER>s list=$lb($c(0),$c(1),"Hello",",","World")
USER>s printable=$system.Encryption.Base64Encode($zconvert(list,"O","UTF8"))
USER>w printable
USER>s list2=$zconvert($system.Encryption.Base64Decode(printable),"I","UTF8")
USER>w list2=list
USER>w $a($li(list2,1))
USER>w $a($li(list2,2))
USER>w $li(list2,3)
USER>w $li(list2,4)
USER>w $li(list2,5)

Note that Base64Encode adds a CRLF after every 76 characters, so if you want to remove these from your "printable" you can either $TR(printable,$c(13,10)) or on 2015.2 or later you can pass a second argument to Base64Encode.

Thanks John, the above terminal transcript is not correct showing what I wanted to show. I've fixed this.

Why can't you understand the purpose of this?

I can only transfer strings by some channel (f.e. interprocess communication). Now I need to send the array of strings (list, object, etc) from sender to receiver. To send this array, I must convert it to the string and then, after receiving, convert it back to array to read it's elements. How to do this in Caché 2013.*? The strings in array can contain any characters, so it is not possible to specify any delimiter character.

Finally I got why the question is pretty confusing for you. Just imagine, I didn't know that $lb() returns the simple string. I didn't know that I can write this string to file, read it from file, and then apply $LISTGET function to it. I didn't know $LISTGET function takes string type. I thought that $LIST is something more than just a string.

So the solution:

set string = $LB(1,2,3,",",5)
/* send this string anywhere */
set element = $LISTGET(string, 4) // = ","

You can use %SerialObject for that:

Class Utils.Serial Extends %SerialObject

Property Payload As %String;

/// zw ##class(Utils.Serial).Test()
ClassMethod Test(input As %String = {$lb(1,2,3,",",5)}) As %String
    set obj = ##class(Utils.Serial).%New()
    set obj.Payload = input
    do obj.%SerializeObject(.str)
    kill (str)
    set obj = ##class(Utils.Serial).%Open(str)
    return obj.Payload

For example:

zw ##class(Utils.Serial).Test("1,2,3,,,5")

zw ##class(Utils.Serial).Test($lb(1,2,3,",",5))