MongoCursor

public class MongoCursor<T> : CursorProtocol where T : Decodable, T : Encodable

A MongoDB cursor.

Note that the next method blocks until a result is received or the cursor is exhausted, so methods inherited from Sequence that iterate over the entire sequence may block indefinitely when used on tailable cursors (e.g. reduce).

It is safe to kill(...) a MongoCursor from another thread while it is blocked waiting on results, however.

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  • Indicates whether this cursor has the potential to return more data.

    This method is mainly useful if this cursor is tailable, since in that case tryNext may return more results even after returning nil.

    If this cursor is non-tailable, it will always be dead after either tryNext returns nil or a non-DecodingError error.

    This cursor will be dead after next returns nil or a non-DecodingError error, regardless of the MongoCursorType.

    This cursor may still be alive after next or tryNext returns a DecodingError.

    Declaration

    Swift

    public func isAlive() -> Bool
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  • id

    Returns the ID used by the server to track the cursor. nil once all results have been fetched from the server.

    Declaration

    Swift

    public var id: Int64? { get }
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  • Returns a Result containing the next T in this cursor, an error if one occurred, or nil if the cursor is exhausted.

    If this cursor is tailable, this method will continue polling until a non-empty batch is returned from the server or the cursor is closed.

    On failure, there error returned is likely one of the following:

    • MongoError.CommandError if an error occurs while fetching more results from the server.
    • MongoError.LogicError if this function is called after the cursor has died.
    • MongoError.LogicError if this function is called and the session associated with this cursor is inactive.
    • DecodingError if an error occurs decoding the server’s response.

    Declaration

    Swift

    public func next() -> Result<T, Error>?

    Return Value

    A Result<T, Error>? containing the next T in this cursor on success, an error if one occurred, or nil if the cursor was exhausted.

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  • Attempt to get the next T from the cursor, returning nil if there are no results.

    If this cursor is tailable, this method may be called repeatedly while isAlive is true to retrieve new data.

    If this cursor is a tailable await cursor, it will wait for results server side for a maximum of maxAwaitTimeMS before returning nil. This option can be configured via options passed to the method that created this cursor (e.g. the maxAwaitTimeMS option on the FindOptions passed to find).

    On failure, there error returned is likely one of the following: - MongoError.CommandError if an error occurs while fetching more results from the server. - MongoError.LogicError if this function is called after the cursor has died. - MongoError.LogicError if this function is called and the session associated with this cursor is inactive. - DecodingError if an error occurs decoding the server’s response.

    Declaration

    Swift

    public func tryNext() -> Result<T, Error>?

    Return Value

    A Result<T, Error>? containing the next T in this cursor on success, an error if one occurred, or nil if there were no results.

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  • Kill this cursor.

    This method may be called from another thread safely even if this cursor is blocked retrieving results. This is mainly useful for freeing a thread that a cursor is blocking via a long running operation.

    This method is automatically called in the deinit of MongoCursor, so it is not necessary to call it manually.

    Declaration

    Swift

    public func kill()
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