build BSON string recursively and re-use for query

[Mick]

In C++ , instead of doing this:

qryStr = QUERY("d" << 1 << "t" << 2 << "l" << "mine");

bsonStr = BSON("d" << 1 << "t" << 2 << "l" << "mine");

 

can I do something like

strStream << "d" << 1 << "t" << 2 << "l" << "mine";

qryStr = QUERY(strStream);

bsonStr = BSON(strStream);

 

I tried defining strStream as stringstream, but it's complaining. 

Is that even possible in C++?

 

Thank you in advance.

[David Hows]

Hi Mick,

The BSON function is actually a macro with a definition of

 #define BSON(x) (( mongo::BSONObjBuilder(64) << x ).obj())

You can build an object by creating a BSONObjBuilder and then just start appending things too it, like so;

BSONObjBuilder query2;

query2.append("d", 1);

query2.append("t", 2);

query2.append("l", "mine");

Finally, when you need to use it for a query just use the .obj() method.

eg conn.query(ns, query2.obj());

Hope that helps,

David

[Mick]

Thank you, David :)

I was under the impression that I had to use QUERY(x) to query mongo, but good to know that I can use BSON(x) instead.

for example: instead of conn.query(dbName, QUERY(x));

I can use conn.query(dbName, BSON(x));

[David Hows]

Absolutely correct.

Both the QUERY macro and the BSON macro provide a BSONObj data type.

Cheers,

David