Powershell conditionally add switch & parameter to function call

Question

I am using a function that has an optional switch, however in a loop, switch and related value may be required or not, depending on a pagination mechanism.

# basic function call
myFunction $someParam 

# function call with pagination switch
myFunction $someParam -NextPageToken $theToken

Ideally this should be used in a more elegant way in a loop:

$theToken = ""
do{
   $result = myFunction $someParam -NextPageToken $theToken # pagination switch should not be used on first call
   $theToken = $result.next_page_token
}while($theToken -ne "")

But the function will throw an error if the switch is used with no value....

Does Powershell support dynamically/conditionally adding the switch & value only if required, so that the function call is used only once in code?

Does not sound like a good function design. Let it return the first token when "" is passed to -NextPageToken or don't use any parameter and just let it return the next token (works only if you don't need to go back). — stackprotector
– stackprotector, Commented May 20, 2020 at 10:13

Mathias R. Jessen · Accepted Answer · 2020-05-20 12:10:54Z

3

Use a hashtable to splat the token:

$params = @{}
do{
   $result = myFunction $someParam @params
   $params = @{ NextPageToken = $result.next_page_token }
}while("" -ne $params['NextPageToken'])

On the first iteration, the splatting table will be empty (ie. no NextPageToken parameter will be passed), but subsequent runs will.

See the about_Splatting help file to learn more about using splatting for conditional parameter arguments

answered May 20, 2020 at 12:10

Mathias R. Jessen

178k13 gold badges175 silver badges234 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Riccardo Over a year ago

Stylish!......... Thanks :-) . Just a question: in your sample, is it intentional to use NextPageToken in place of -NextPageToken ?

Mathias R. Jessen Over a year ago

@Riccardo Yes that's intentional - the hashtable key must match the name of the parameter - and the - we use in normal command syntax is not part of the name itself

Collectives™ on Stack Overflow

Powershell conditionally add switch & parameter to function call

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related