add custom SQLA filter example

examples/custom-sqla-filter/README.rst

+Custom filter with SQLAlchemy backend example.
+
+To run this example:
+
+1. Clone the repository::
+
+  git clone https://github.com/mrjoes/flask-admin.git
+  cd flask-admin
+
+2. Create and activate a virtual environment::
+
+  virtualenv env
+  source env/bin/activate
+
+3. Install requirements::
+
+  pip install -r 'examples/custom-filter/requirements.txt'
+
+4. Run the application::
+
+  python examples/custom-filter/app.py
+
+The first time you run this example, a sample sqlite database gets populated automatically. To suppress this behaviour,
+comment the following lines in app.py:::
+
+  if not os.path.exists(database_path):
+      build_sample_db()

examples/custom-sqla-filter/__init__.py

+

examples/custom-sqla-filter/app.py

+from flask import Flask
+from flask.ext.sqlalchemy import SQLAlchemy
+
+from flask.ext.admin.contrib import sqla
+from flask.ext.admin import expose, Admin
+
+# required for creating custom filters
+from flask.ext.admin.contrib.sqla.filters import BaseSQLAFilter, FilterEqual
+
+# Create application
+app = Flask(__name__)
+
+# Create dummy secrey key so we can use sessions
+app.config['SECRET_KEY'] = '123456790'
+
+# Create in-memory database
+app.config['DATABASE_FILE'] = 'sample_db.sqlite'
+app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///' + app.config['DATABASE_FILE']
+app.config['SQLALCHEMY_ECHO'] = True
+db = SQLAlchemy(app)
+
+# Create model
+class User(db.Model):
+    def __init__(self, first_name, last_name, username, email):
+        self.first_name = first_name
+        self.last_name = last_name
+        self.username = username
+        self.email = email
+    
+    id = db.Column(db.Integer, primary_key=True)
+    first_name = db.Column(db.String(100))
+    last_name = db.Column(db.String(100))
+    username = db.Column(db.String(80), unique=True)
+    email = db.Column(db.String(120), unique=True)
+
+    # Required for administrative interface. For python 3 please use __str__ instead.
+    def __unicode__(self):
+        return self.username
+
+# Create custom filter class
+class FilterLastNameBrown(BaseSQLAFilter):
+    def apply(self, query, value):
+        if value == '1':
+            return query.filter(self.column == "Brown")
+        else:
+            return query.filter(self.column != "Brown")
+
+    def operation(self):
+        return 'is Brown'
+
+# Add custom filter and standard FilterEqual to ModelView
+class UserAdmin(sqla.ModelView):
+    # each filter in the list is a filter operation (equals, not equals, etc)
+    # filters with the same name will appear as operations under the same filter
+    column_filters = [
+        FilterEqual(User.last_name, 'Last Name'), 
+        FilterLastNameBrown(User.last_name, 'Last Name', options=(('1', 'Yes'),('0', 'No')))
+    ]
+    
+admin = Admin(app, template_mode="bootstrap3")
+admin.add_view(UserAdmin(User, db.session))
+
+def build_sample_db():
+    db.drop_all()
+    db.create_all()
+    user_obj1 = User("Paul", "Brown", "pbrown", "paul@gmail.com")
+    user_obj2 = User("Luke", "Brown", "lbrown", "luke@gmail.com")
+    user_obj3 = User("Serge", "Koval", "skoval", "serge@gmail.com")
+        
+    db.session.add_all([user_obj1, user_obj2, user_obj3])
+    db.session.commit()
+
+if __name__ == '__main__':
+    build_sample_db()
+    app.run(port=5000)
\ No newline at end of file

examples/custom-sqla-filter/requirements.txt

+Flask
+Flask-Admin
+Flask-SQLAlchemy