Select
Select( path, from, default )
Select( path, from, default )
Select( path, from, default )
Select( path, from, default )
select( path, from, default )
Select( path, from, default )
Description
The Select
function extracts a single value from a document. It
extracts the value specified by the path
parameter out of the from
parameter and returns the value. If the path
does not exist, the
optional default
object is returned. If the default object is not
provided, an error is returned.
Parameter
Argument | Type | Definition and Requirements |
---|---|---|
|
Long or String |
The path to a field in the document to extract. |
|
Object |
The object containing the data to be extracted. |
|
Object |
Optional - The value to be returned if the path does not exist. |
Examples
The following query extracts from the top level object named "favorites" and second level array called "foods" the value in position 1 of the array. This value is "munchings".
try
{
Value result = await client.Query(
Select(
Arr("favorites", "foods", 1),
Obj(
"favorites", Obj("foods", Arr("crunchings", "munchings", "lunchings"))
)
)
);
Console.WriteLine(result);
}
catch (Exception e)
{
Console.WriteLine($"ERROR: {e.Message}");
}
StringV(munchings)
result, err := client.Query(
f.Select(
f.Arr{"favorites", "foods", 1},
f.Obj{
"favorites": f.Obj{
"foods": f.Arr{"crunchings", "munchings", "lunchings"}}}))
if err != nil {
fmt.Fprintln(os.Stderr, err)
} else {
fmt.Println(result)
}
munchings
System.out.println(
client.query(
Select(
Arr(Value("favorites"), Value("foods"), Value(1)),
Obj(
"favorites", Obj(
"foods", Arr(
Value("crunchings"),
Value("munchings"),
Value("lunchings")
)
)
)
)
).get());
"munchings"
client.query(
q.Select(
['favorites', 'foods', 1],
{ favorites: { foods: ['crunchings', 'munchings', 'lunchings'] } },
)
)
.then((ret) => console.log(ret))
.catch((err) => console.error('Error: %s', err))
munchings
result = client.query(
q.select(
["favorites", "foods", 1],
{
"favorites": {"foods": ["crunchings", "munchings", "lunchings"]}
}
)
)
print(result)
munchings
try {
println(Await.result(
client.query(
Select(
Arr("favorites", "foods", 1),
Obj(
"favorites" -> Obj("foods" -> Arr("crunchings", "munchings", "lunchings"))
))),
5.seconds
))
} catch {
case unknown: Throwable => println("Error: " + unknown.getMessage())
}
"munchings"
The following example uses Select
to extract the "id" attribute
from the Reference.
try
{
Value result = await client.Query(
Select(Arr("id"), Database("prydain"))
);
Console.WriteLine(result);
}
catch (Exception e)
{
Console.WriteLine($"ERROR: {e.Message}");
}
StringV(prydain)
result, err := client.Query(
f.Select(f.Arr{"id"}, f.Database("prydain")))
if err != nil {
fmt.Fprintln(os.Stderr, err)
} else {
fmt.Println(result)
}
prydain
System.out.println(
client.query(
Select(Arr(Value("id")), Database(Value("prydain")))
).get());
"prydain"
client.query(
q.Select(['id'], q.Database('prydain'))
)
.then((ret) => console.log(ret))
.catch((err) => console.error('Error: %s', err))
prydain
result = client.query(
q.select(["id"], q.database("prydain"))
)
print(result)
prydain
try {
println(Await.result(
client.query(Select(Arr("id"), Database("prydain"))),
5.seconds
))
} catch {
case unknown: Throwable => println("Error: " + unknown.getMessage())
}
"prydain"
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