Find, First, Last, Offset, Limit

You may want to fetch one model instead of a collection.

Find

Collection#find allows to fetch a model based on an expression.

There's two flavors for find method: find and find! . The first one return a nilable type, which will be nil if not found, while the second return a model or throw an exception if not found.

Example

p = Product.query.find({id: 1234}) # Return Product?

p = Product.query.find!{ id == 1234 } # Return Product or throw an exception if not found.

First / Last

First and last return the first and last row of a SELECT query.

In the case of first, it will order by [primary key column] ASC if no order_by directive is found. In the case of last, it will invert the direction of the order directive, turning each ASC to DESC and vice-versa before performing the call.

Both return a model instead of an enumeration of models.

# SELECT * FROM products ORDER BY created_at ASC LIMIT 1
p = Product.query.order_by("created_at", "DESC").last!

# SELECT * FROM products ORDER BY created_at DESC LIMIT 1
p = Product.query.order_by("created_at", "DESC").first!

Like with find, first!/first and last/last! are existing variant of the method

Offset and Limit

Offset and limit provide a way to scope a request or do some pagination.

Offset

Product.query.order_by("id").limit(5).offset(5)

The code above will fetch the model from position 5 .. 10 of the query.

It is possible to write the same behavior as above by using [] operator:

products = Product.query.order_by("id")[5..10]

Nothing to be aware: [] operator will resolve the query, calling it and return an Array of model, not a Collection object anymore.

You may use the [] operator with a number as parameter instead of range. In this case, it's equivalent to offset(number).first!. The []? operator is equivalent to offset(number).first and will return nilable reference.