Firestore/src/V1beta1/Write.php
public function setUpdateMask($var)
    {
        GPBUtil::checkMessage($var, \Google\Cloud\Firestore\V1beta1\DocumentMask::class);
        $this->update_mask = $var;

        return $this;
    }
public function setUpdateMask($var)
    {
        GPBUtil::checkMessage($var, \Google\Cloud\Firestore\V1beta1\DocumentMask::class);
        $this->update_mask = $var;

        return $this;
    }
public function setUpdateMask ( $ var ) { GPBUtil :: checkMessage ( $ var , \ Google \ Cloud \ Firestore \ V1beta1 \ DocumentMask :: class ) ; $ this -> update_mask = $ var ; return $ this ; }
The fields to update in this write.
This field can be set only when the operation is `update`.
If the mask is not set for an `update` and the document exists, any
existing data will be overwritten.
If the mask is set and the document on the server has fields not covered by
the mask, they are left unchanged.
Fields referenced in the mask, but not present in the input document, are
deleted from the document on the server.
The field paths in this mask must not contain a reserved field name.

Generated from protobuf field <code>.google.firestore.v1beta1.DocumentMask update_mask = 3;</code>
@param \Google\Cloud\Firestore\V1beta1\DocumentMask $var
@return $this
The fields to update in this write . This field can be set only when the operation is update . If the mask is not set for an update and the document exists any existing data will be overwritten . If the mask is set and the document on the server has fields not covered by the mask they are left unchanged . Fields referenced in the mask but not present in the input document are deleted from the document on the server . The field paths in this mask must not contain a reserved field name .