How can I find the value of nested values of only field data in rethinkDB?
My first concatMap returns something like the following. I would like to get the value "d", so the value will be "Rethinkdb"
[
{
"a":{
"b":{
"c":"NoSQL",
"d":"Rethinkdb"
}
}
},
{
"a":{
"b":"text"
}
},
{
"a":{
"b":"another"
}
}
]
I've tried like r.(...).concatMap(function(f){return f("a")("b")("d")})
But the displayed error is RqlRuntimeError: Can't execute parentheses for non-sequence non-objects (that's because there is no "d" in 2nd and 3rd "b"). I cannot use nth
because "d" will not always be the first element of the array.
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You should take a look at the method hasFields
and check the possibility of nested properties using boolean. There's a very good example of this scenario in the docs.
I would get all the documents that have the fields I want and then do concatMap
.
r.table('')
// Get all documents with a value in property in `a.b.d`
// `true` here doesn't refer to the value of the property,
// but to its existence
.hasFields({ a: { b: { d: true } } })
.concatMap(function (row) {
return [ row('a')('b')('d') ];
})
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