Extracting values with jq only when they exist - jq

Question

I have a large file of records that contain fields that look something like this:
{
"id": "1000001",
"updatedDate": "2018-12-21T01:52:00Z",
"createdDate": "1993-11-30T02:59:25Z",
"varFields": [
{
"fieldTag": "b",
"content": "1000679727"
},
{
"fieldTag": "v",
"content": "v.1"
}
}
I need to extract the .content element along with other things, but only when the fieldTag associated with it is "v". Only some records contain a fieldTag "v".
When I try to parse using
(.varFields[] |select(.fieldTag=="v") | "\(.content)") // ""
it works fine so long as v is present. However, when it is not present, I get
jq: error (at <stdin>:353953): Cannot iterate over null (null)
I tried to get rid of the error with multiple variations, including things to the effect of
(select((.varFields[] |select(.fieldTag=="v") | .content) != null) | .varFields[] |select(.fieldTag=="v") | "\(.content)") // ""
but I'm still getting the same error. What am I missing?

Answer 1

Take a look at the error suppression operator ? that works a bit like the new ?. nullable chaining operator in Javascript.
The ? operator, used as EXP?, is shorthand for try EXP.
Example:
jq '[.[]|(.a)?]'
Input [{}, true, {"a":1}]
Output [null, 1]
They have a slightly simpler demonstrable example of this at https://jqplay.org/jq?q=%5B.%5B%5D%7C(.a)%3F%5D&j=%5B%7B%7D%2C%20true%2C%20%7B%22a%22%3A1%7D%5D and the try-catch operator is similar if all you need is custom error handling (or just error ignoring...).