NewBie's Corner Session 20 Parameters and Status Part I

NewBie's Corner Session 20 Parameters and Status Part I

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Parameters

Parameters are another name for Variables when used in passing data from one Routine to another.

Let us say we have 2 routines (RtnA and RtnB), and we want to pass 3 parameters (Parm1, Parm2, Parm3) from RtnA to RtnB.

RtnA would look like:

RtnA

                Set Parm1 = "Value for Parm1"

                Set Parm2 = "Value for Parm2"

                Set Parm3 = "Value for Parm3"

                Do ^RtnB(Parm1, Parm2, Parm3)               ; Actual Call List

                Quit

RtnB would look like:

RtnB(Parm1, Parm2, Parm3)                        ; Formal Call List

                Write !,"Parm1 = ",Parm1

                Write !,"Parm2 = ",Parm2

                Write !,"Parm3 = ",Parm3

                Quit

Actual Call List and Formal Call List   

When RtnA calls RtnB with the three parameters, this is referred to as the "Actual Call List."

When RtnB receives the three parameters, this is referred to as the "Formal Call List."

The number of parameters in the Actual Call List should match the number of parameters in the Formal Call List. (This is not a hard and fast rule, see the InterSystems documentation for exceptions to this rule.)

In addition to passing parameters, a Status can be passed back, see the new RtnA and RtnB below.

RtnA would look like:

RtnA

                Set Var1 = "Value for Var1"

                Set Var2 = "Value for Var2"

                Set Var3 = "Value for Var3"

                Set Status = $$^RtnB(Var1, Var2, Var3)   ; Call to RtnB and receive a Status in return

                Quit

RtnB would look like:

RtnB(Var1, Var2, Var3)

                Write !,"Var1 = ",Var1

                Write !,"Var2 = ",Var2

                Write !,"Var3 = ",Var3

                Set Status = 1

                Quit Status          ; Quit passing back a Status

In RtnA please note, the call to RtnB is not just a "Do" but a "Set Status = ".

And two dollar signs now precede ^RtnB, to give $$^RtnB.

User Defined Function

RtnB now becomes a User Defined Function since it returns a value.

And in RtnB the "Quit Status" passes back the Status.

Successful Status and Unsuccessful Status

By convention when the first character of the Status is a 1, that signifies a success.

And when the first character of the Status is a 0 (Zero), that signifies a failure.

--Mike Kadow

PaulMikeKadow@gmail.com

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