diff options
Diffstat (limited to 'odb-examples/inverse/README')
-rw-r--r-- | odb-examples/inverse/README | 74 |
1 files changed, 74 insertions, 0 deletions
diff --git a/odb-examples/inverse/README b/odb-examples/inverse/README new file mode 100644 index 0000000..493b0d1 --- /dev/null +++ b/odb-examples/inverse/README @@ -0,0 +1,74 @@ +This example shows how to declare and use bidirectional one-to-one, one-to- +many, and many-to-many relationships between persistent objects. It also +shows how to work with lazy pointers. All the relationships presented in +this example declare one side as inverse in order to produce canonical +database schema. + +The example consists of the following files: + +employee.hxx + Header file defining the 'employee', 'employer', 'position', and 'project' + persistent classes as well as the employer-employee (one-to-many), + employee-position (one-to-one), and employee-project (many-to-many) + bidirectional relationships between them. + +employee-odb.hxx +employee-odb.ixx +employee-odb.cxx +employee.sql + The first three files contain the database support code and the last file + contains the database schema for the employee.hxx header. + + These files are generated by the ODB compiler from employee.hxx using the + following command line: + + odb --std c++11 -d <database> --generate-schema --generate-query \ + --generate-session --default-pointer std::shared_ptr employee.hxx + + Where <database> stands for the database system we are using, for example, + 'pgsql'. + + The --generate-session option is used to enable session support for all + the persistent classes in employee.hxx. The --default-pointer option is + used to make std::shared_ptr the default object pointer. + +database.hxx + Contains the create_database() function which instantiates the concrete + database class corresponding to the database system we are using. + +driver.cxx + Driver for the example. It includes the employee.hxx and employee-odb.hxx + headers to gain access to the persistent classes and their database support + code. It also includes database.hxx for the create_database() function + declaration. + + In main() the driver first calls create_database() to obtain the database + instance. It then creates a number of 'employee', 'employer', 'position', + and 'project' objects, sets the relationships between them, and persists + them in the database. In the next few transactions the driver loads various + objects, then accesses and modifies the relationships between them. Finally, + the driver performs a database query which uses a data member from a related + object in its criterion. + +To compile and link the example manually from the command line we can use the +following commands (using PostgreSQL as an example; replace 'c++' with your +C++ compiler name): + +c++ -c employee-odb.cxx +c++ -DDATABASE_PGSQL -c driver.cxx +c++ -o driver driver.o employee-odb.o -lodb-pgsql -lodb + +To run the example we may first need to create the database schema (for some +database systems, such as SQLite, the schema is embedded into the generated +code which makes this step unnecessary). Using PostgreSQL as an example, this +can be achieved with the following command: + +psql --username=odb_test --dbname=odb_test -f employee.sql + +Here we use 'odb_test' as the database login and also 'odb_test' as the +database name. + +Once the database schema is ready, we can run the example (using PostgreSQL as +the database): + +./driver --user odb_test --database odb_test |