Powershell: Using Invoke-WebRequest, How To Use Variable Within JSON?

Question

Using Powershell, I'm trying to PUT data into an API, but I'm having trouble using a variable within the JSON:

This code below does not generate an error from the API, but it PUTS the singer as, literally, "$var_currentsinger" and doesn't use the intended variable

$currentsinger = "Michael Jackson"
$headers.Add("Content-Type", "application/json")
$response = Invoke-WebRequest -Uri https://stackoverflow.com -Method PUT -Headers $headers -Body '{
  "album": {
    "name": "Moonlight Sonata",
    "custom_fields": [{
      "singer": "$currentsinger",
      "songwriter": "Etta James"
    }]
  }
}'

This version below does not work, I assume because there are no quotes around the singer name. The API returns a value that the data is invalid

$currentsinger = "Michael Jackson"
$headers.Add("Content-Type", "application/json")
$response = Invoke-WebRequest -Uri https://stackoverflow.com -Method PUT -Headers $headers -Body '{
  "album": {
    "name": "Moonlight Sonata",
    "custom_fields": [{
      "singer": $currentsinger,
      "songwriter": "Etta James"
    }]
  }
}'

The only thing I have tried is double quotes and triple quotes around the variable, but I either get the $currentsinger variable within the JSON and have it submit the variable value and not the variable name.

json often (always?) only allows double-quotes. You can escape each internal double-quote with backtick, or join single-quoted strings together — Cpt.Whale
– Cpt.Whale, Commented May 25, 2022 at 19:33
@Cpt.Whale Can you make that an answer? I don't know if I understand how to implement what you're saying to try. — Beems
– Beems, Commented May 25, 2022 at 20:35
@Cpt.Whale I got it done based on your advice. Please make it an answer and I'll accept it. I ended up doing backtickdoublequote for each internal double quote (too hard to put as inline comment code, so I'll paste my final code once you post as an answer) — Beems
– Beems, Commented May 25, 2022 at 20:48
Instead of generating the json text yourself, consider creating a nested hashtable and using ConvertTo-Json as it will handle a whole multitude of edge-case for you - for example, what if $currentsinger = “James `”Godfather of Soul`” Brown” - you’d end up with invalid json by just interpolating the variable value into a json string — mclayton
– mclayton, Commented May 26, 2022 at 8:15

Cpt.Whale · Accepted Answer · 2022-05-26 13:42:07Z

2

JSON requires double-quotes, so one example way to handle is by escaping the quotes or with a double-quoted here-string:

# here-string
$json = @"
  "singer": $currentsinger,
  "songwriter": "Etta James"
"@

# escaped
$json = "
  `"singer`": $currentsinger,
  `"songwriter`": `"Etta James`"
"

answered May 26, 2022 at 13:42

Cpt.Whale

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