EEx v1.9.1 EEx.Engine behaviour View Source

Basic EEx engine that ships with Elixir.

An engine needs to implement all callbacks below.

An engine may also use EEx.Engine to get the default behaviour but this is not advised. In such cases, if any of the callbacks are overridden, they must call super() to delegate to the underlying EEx.Engine.

Link to this section Summary

Types

state()

Functions

handle_assign(arg)

Handles assigns in quoted expressions.

Callbacks

handle_begin(state)

Invoked at the beginning of every nesting.

handle_body(state)

Called at the end of every template.

handle_end(state)

Invokes at the end of a nesting.

handle_expr(state, marker, expr)

Called for the dynamic/code parts of a template.

handle_text(state, text)

Called for the text/static parts of a template.

init(opts)

Called at the beginning of every template.

Link to this section Types

state()

Specs

state() :: term()

Link to this section Functions

handle_assign(arg)

Specs

handle_assign(Macro.t()) :: Macro.t()

Handles assigns in quoted expressions.

A warning will be printed on missing assigns. Future versions will raise.

This can be added to any custom engine by invoking handle_assign/1 with Macro.prewalk/2:

def handle_expr(state, token, expr) do
  expr = Macro.prewalk(expr, &EEx.Engine.handle_assign/1)
  super(state, token, expr)
end

Link to this section Callbacks

handle_begin(state)

Specs

handle_begin(state()) :: state()

Invoked at the beginning of every nesting.

It must return a new state that is used only inside the nesting. Once the nesting terminates, the current state is resumed.

handle_body(state)

Specs

handle_body(state()) :: Macro.t()

Called at the end of every template.

It must return Elixir's quoted expressions for the template.

handle_end(state)

Specs

handle_end(state()) :: Macro.t()

Invokes at the end of a nesting.

It must return Elixir's quoted expressions for the nesting.

handle_expr(state, marker, expr)

Specs

handle_expr(state(), marker :: String.t(), expr :: Macro.t()) :: state()

Called for the dynamic/code parts of a template.

The marker is what follows exactly after <%. For example, <% foo %> has an empty marker, but <%= foo %> has "=" as marker. The allowed markers so far are:

""
"="
"/"
"|"

Markers "/" and "|" are only for use in custom EEx engines and are not implemented by default. Using them without an appropriate implementation raises EEx.SyntaxError.

It must return the updated state.

handle_text(state, text)

Specs

handle_text(state(), text :: String.t()) :: state()

Called for the text/static parts of a template.

It must return the updated state.

init(opts)

Specs

init(opts :: keyword()) :: state()

Called at the beginning of every template.

It must return the initial state.