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11 Note the value of userupdated_at Told you the timestamp was in UTC
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User Model
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>> foo => #<User id: 3, name: "Foo", email: "foo@barcom", created_at: "2010-01-05 01:05:42", updated_at: "2010-01-05 01:05:42">
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How do we know if we really destroyed an object And for saved and non-destroyed objects, how can we retrieve users from the database It s time to learn how to use Active Record to find user objects
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614 Finding User Objects
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Active Record provides several options for finding objects Let s use them to find the first user we created while verifying that the third user (foo) has been destroyed We ll start with the existing user:
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>> Userfind(1) => #<User id: 1, name: "Michael Hartl", email: "mhartl@examplecom", created_at: "2010-01-05 00:57:46", updated_at: "2010-01-05 00:57:46">
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Here we ve passed the id of the user to Userfind; Active Record returns the user with that id attribute Let s see if the user with an id of 3 still exists in the database:
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>> Userfind(3) ActiveRecord::RecordNotFound: Couldn't find User with ID=3
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Since we destroyed our third user in Section 613, Active Record can t find it in the database Instead, find raises an exception, which is a way of indicating an exceptional event in the execution of a program in this case, a nonexistent Active Record id, which causes find to raise an ActiveRecord::RecordNotFound exception12 In addition to the generic find, Active Record also allows us to find users by specific attributes:
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12 Exceptions and exception handling are somewhat advanced Ruby subjects, and we won t need them much in this book They are important, though, and I suggest learning about them using one of the Ruby books recommended in Section 111
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6: Modeling and Viewing Users, Part I
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>> Userfind_by_email("mhartl@examplecom") => #<User id: 1, name: "Michael Hartl", email: "mhartl@examplecom", created_at: "2010-01-05 00:57:46", updated_at: "2010-01-05 00:57:46">
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Since we will be using email addresses as usernames, this sort of find will be useful when we learn how to let users sign in to our site ( 8)13 We ll end with a couple of more general ways of finding users First, there s first:
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>> Userfirst => #<User id: 1, name: "Michael Hartl", email: "mhartl@examplecom", created_at: "2010-01-05 00:57:46", updated_at: "2010-01-05 00:57:46">
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Naturally, first just returns the first user in the database There s also all:
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>> Userall => [#<User id: 1, name: "Michael Hartl", email: "mhartl@examplecom", created_at: "2010-01-05 00:57:46", updated_at: "2010-01-05 00:57:46">, #<User id: 2, name: "A Nother", email: "another@exampleorg", created_at: "2010-01-05 01:05:24", updated_at: "2010-01-05 01:05:24">]
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No prizes for inferring that all returns an array (Section 431) of all users in the database
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615 Updating User Objects
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Once we ve created objects, we often want to update them There are two basic ways to do this First, we can assign attributes individually, as we did in Section 445:
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>> user # Just a reminder about our user's attributes => #<User id: 1, name: "Michael Hartl", email: "mhartl@examplecom", created_at: "2010-01-05 00:57:46", updated_at: "2010-01-05 00:57:46"> >> useremail = "mhartl@examplenet" => "mhartl@examplenet" >> usersave => true
13 To those worried that find_by_email will be inefficient if there are a large number of users, you re ahead of the game We ll cover this issue, and its solution via database indices, in Section 624
User Model
Note that the final step is necessary to write the changes to the database We can see what happens without a save by using reload, which reloads the object based on the database information:
>> => >> => >> =>
useremail "mhartl@examplenet" useremail = "foo@barcom" "foo@barcom" userreloademail "mhartl@examplenet"
Now that we ve updated the user, the magic columns differ, as promised in Section 613:
>> => >> =>
usercreated_at "2010-01-05 00:57:46" userupdated_at "2010-01-05 01:37:32"
The second way to update attributes is to use update_attributes:
>> => >> => >> =>
userupdate_attributes(:name => "The Dude", :email => "dude@abidesorg") true username "The Dude" useremail "dude@abidesorg"
The update_attributes method accepts a hash of attributes, and on success performs both the update and the save in one step (returning true to indicate that the save went through) It s worth noting that, once you have defined some attributes as accessible using attr_accessible (Section 612), only those attributes can be modified using update_attributes If you ever find that your models mysteriously start refusing to update certain columns, check to make sure that those columns are included in the call to attr_accessible