6.1 play with the newly created model.
in prev chapter, we created a user model, now we will play with it.
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1. first, let's start rails console,
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this time we will use a param: --sandbox
this param make sure when you exit the console, all changes made here will be rolled back!!!
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rails console --sandbox
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(if you want to play with test database, you can
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rails console test
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2. I have a very good habit that when play with the console, I will keep a log terminal open, to see what is happening on the log.
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use this command to power up the log terminal:
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tail -f log/development.log
-f param will make sure it will add newly added lines to the terminal when new lines created.
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3. after you start rails console, Rails will auto load rails environment, so models and controllers are all loaded.
you can use them directly
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4. for a model that inherit from active record, you can initialize it using a hash that include the value of the attributs.
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for example:
user = User.new(:name => "abcd", :email => "abcd@abcd.com")
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to save this record, you need to call:
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user.save
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this line will save the user info into database.
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this method return true if save successful, return false if the save fails.
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5. user = User.new
user.save
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these two lines can create and save a user record.
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there is anoter way that will create and save by one line of code:
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user = User.create(:name => "abcd", :email => "abcd@abcd.com")
note: User.create will return the object itself.
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6. the opposite side of User.create is?user_object.destroy
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user.destroy
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this method will also return the destroied user object.
(but in general, I have never find this returned destroied object of any use. this object is still in memory after destroy)
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7. next we will learn "find" method that will be used everyday:
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a. User.find(1) =======> find by user id
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b. ?a more genral use of find is finding by a colum:
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User.find_by_email "abcd@abcd.com"
(but, will the effieciency very slow to search through database by find by email? you are right, we will solve it by adding index to database later!!!)
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c. User.first, this is another find.
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d. User.all, this will return an array.
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8. ?next we will learn how to update user object.
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a. user = User.find_by_email "abcd@abcd.com"
user.name = "abcd2"
user.save
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note, "user.save" is need to save it into database!!!
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without it, it will not get saved, we can see this fact by using user.reload:
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user = User.find_by_email "abcd@abcd.com"
user.name = "abcd3"
user.reload.name ? ====> "abcd",?
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b. another way of updating user object is using a method called, update_attributes
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user.update_attributes(:name => "def", :email ?=> "ghz@ghz.com" )
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will return true if update success
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this method will accept a hash as param, using the hash to update records.
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one thing to note: ?if you used to define any attr_accessible attributes, then only columns that belong to attr_accessible can be updated using this method
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