sequence.has_fields([selector1, selector2...]) → stream array.has_fields([selector1, selector2...]) → array object.has_fields([selector1, selector2...]) → boolean
Test if an object has one or more fields. An object has a field if it has that key and the key has a non-null value. For instance, the object {'a':1,'b':2,'c':null} has the fields a and b.
When applied to a single object, has_fields returns true if the object has the fields and false if it does not. When applied to a sequence, it will return a new sequence (an array or stream) containing the elements that have the specified fields.
Example: Return the players who have won games.
r.table('players').has_fields(:games_won).run(conn)
Example: Return the players who have not won games. To do this, use has_fields with not, wrapped with filter.
r.table('players').filter { |row| row.has_fields(:games_won).not }.run(conn)
Example: Test if a specific player has won any games.
r.table('players').get(
'b5ec9714-837e-400c-aa74-dbd35c9a7c4c'
).has_fields(:games_won).run(conn)
Nested Fields
has_fields lets you test for nested fields in objects. If the value of a field is itself a set of key/value pairs, you can test for the presence of specific keys.
Example: In the players table, the games_won field contains one or more fields for kinds of games won:
{
:games_won => {
:playoffs => 2,
:championships => 1
}
}
Return players who have the “championships” field.
r.table('players').has_fields(
{:games_won => {:championships => true}}
).run(conn)
Note that true in the example above is testing for the existence of championships as a field, not testing to see if the value of the championships field is set to true. There’s a more convenient shorthand form available. (See pluck for more details on this.)
r.table('players').has_fields({:games_won => :championships}).run(conn)
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