### problems
```ruby
class Address < ActiveRecord::Base
  belongs_to :customer
end

class Customer <ActiveRecord::Base
  has_one :address
  has_many :invoices
end

class Invoice < ActiveRecord::Base
  belongs_to :customer
end
```

```html
<%= @invoice.customer.name %>
<%= @invoice.customer.address.city %>
<%= @invoice.customer.address.street %>
<%= @invoice.customer.address.state %>
```
### solutions
1. use only one dot
```ruby
class Address < ActiveRecord::Base
  belongs_to :customer
end

class Customer < ActiveRecord::Base
  has_one :address
  has_many :invoices

  def street
    address.street
  end

  def city
    address.city
  end
end

class Invoice < ActiveRecord::Base
  belongs_to :customer

  def customer_name
    customer.name
  end

  def customer_street
    customer.street
  end

  def customer_city
    customer.city
  end
end
```

```html
  <%= @invoice.customer_name %>
  <%= @invoice.customer_city %>
  <%= @invoice.customer_street %>
```

> tooo many methods