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<p class='prelude'><span></span></p>
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<h1><span>Phoenix: Ecto models</span></h1>
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<div class='post-content -cheatsheet'>
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<p>This is for Phoenix 1.2 and below. <a href="phoenix-ecto@1.3.html">Phoenix 1.3 has a new API.</a>.</p>
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<h2 id="generating">Generating</h2>
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<pre><code>$ mix phoenix.gen.html Profile profiles email:string age:integer
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$ mix phoenix.gen.html User users email:string hashed_password:string
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</code></pre>
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<h2 id="schema">Schema</h2>
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<pre><code class="language-elixir">defmodule User do
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use Ecto.Schema
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schema "users" do
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field :name
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field :age, :integer
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# :id :binary :integer :float :boolean :string :binary
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# {:array, inner_type} :decimal :map
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field :password, virtual: true
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end
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end
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</code></pre>
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<h2 id="changesets">Changesets</h2>
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<pre><code class="language-elixir">def changeset(user, params \\ :empty) do
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%User{}
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|> Ecto.Changeset.change # basic casting to changeset
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user
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|> cast(params, ~w(name email), ~w(age)) # params to Changeset
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|> validate_format(:email, ~r/@/)
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|> validate_inclusion(:age, 18..100)
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|> validate_exclusion(:role, ~w(admin superadmin))
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|> validate_subset(:pets, ~w(cat dog parrot whale))
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|> validate_length(:body, min: 1)
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|> validate_length(:body, min: 1, max: 160)
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|> validate_length(:partners, is: 2)
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|> validate_number(:pi, greater_than: 3)
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|> validate_number(:pi, less_than: 4)
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|> validate_number(:pi, equal_to: 42)
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|> validate_change(:title, fn _, _ -> [])
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|> validate_confirmation(:password, message: "does not match")
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|> unique_constraint(:email)
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|> foreign_key_constraint(:post_id)
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|> assoc_constraint(:post) # ensure post_id exists
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|> no_assoc_constraint(:post) # negative (useful for deletions)
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end
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</code></pre>
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<pre><code class="language-elixir">changeset.valid?
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changeset.errors #=> [title: "empty"]
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changeset.changes #=> %{}
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changeset.params[:title]
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changeset.required #=> [:title]
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changeset.optional #=> [:body]
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</code></pre>
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<h3 id="updating">Updating</h3>
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<pre><code class="language-elixir">changeset #(or model)
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|> change(title: "New title")
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|> change(%{ title: "New title" })
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|> put_change(:title, "New title")
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|> force_change(:title, "New title")
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|> update_change(:title, &(&1 <> "..."))
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|> delete_change(:title)
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|> merge(other_changeset)
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|> add_error(:title, "empty")
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</code></pre>
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<h3 id="getting">Getting</h3>
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<pre><code class="language-elixir">get_change(changeset, :title) #=> "hi" (if changed)
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get_field(changeset, :title) #=> "hi" (even if unchanged)
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fetch_change(changeset, :title) #=> {:ok, "hi"} | :error
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fetch_field(changeset, :title) #=> {:changes | :model, "value"} | :error
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</code></pre>
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<h2 id="ecto">Ecto</h2>
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<h3 id="get-one">Get one</h3>
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<pre><code class="language-elixir">Repo.get(User, id)
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Repo.get_by(User, email: "john@hello.com") #=> %User{} | nil
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# also get! get_by!
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</code></pre>
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<h3 id="createupdate">Create/update</h3>
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<pre><code class="language-elixir">changeset |> Repo.update
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changeset |> Repo.insert
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changeset |> Repo.insert_or_update
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</code></pre>
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<pre><code>User
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|> Ecto.Changeset.change(%{name: "hi"})
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|> Repo.insert
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</code></pre>
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<h2 id="many">Many</h2>
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<h3 id="queries">Queries</h3>
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<pre><code class="language-elixir">from p in Post,
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where: p.title == "Hello",
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where: [state: "Sweden"],
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limit: 1,
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offset: 10,
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order_by: c.name,
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order_by: [c.name, c.title],
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order_by: [asc: c.name, desc: c.title],
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preload: [:comments],
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preload: [comments: {c, likes: l}],
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join: c in assoc(c, :comments),
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join: p in Post, on: c.post_id == p.id,
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group_by: p,
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select: p,
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select: {p.title, p.description},
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select: [p.title, p.description],
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</code></pre>
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<h3 id="get-many">Get many</h3>
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<pre><code class="language-elixir">Repo.all(User)
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</code></pre>
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<h3 id="update-many">Update many</h3>
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<pre><code class="language-elixir">Repo.update_all(Post, set: [title: "Title"])
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Repo.update_all(Post, inc: [views: 1])
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</code></pre>
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<h3 id="chaining-_all-with-queries">Chaining <code>_all</code> with queries</h3>
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<pre><code class="language-elixir">from(p in Post, where: p.id < 10)
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|> Repo.update_all(...)
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from(p in Post, where: p.id < 10)
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|> Repo.all()
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</code></pre>
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<strong><a href=".">Devhints.io cheatsheets</a></strong> is a collection of cheatsheets I've written over the years.
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Suggestions and corrections? <a href='https://github.com/rstacruz/cheatsheets/issues/907'>Send them in</a>.
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<i class='fleuron'></i>
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I'm <a href="http://ricostacruz.com">Rico Sta. Cruz</a>.
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Check out my <a href="http://ricostacruz.com/til">Today I learned blog</a> for more.
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