prefer_typedefs_for_callbacks

v1.0.0WarningConfigurableType Annotations

This rule flags an inline function type written where a typedef would name it.

void Function(String, int, bool) tells the reader the shape and nothing else — what the String is, what the bool means, and whether two such parameters are the same concept. A typedef gives the signature a name that can be reused, documented and searched for.

Only function types with at least min_parameters parameters are reported. void Function() and void Function(String) are already readable, and naming them adds indirection without adding information — which is why Flutter’s own VoidCallback and ValueChanged<T> exist for exactly the shapes that clear this bar.

This rule is in the pedantic preset.

Don’t

void listen(void Function(String, int) onEvent) {}

Do

typedef EventHandler = void Function(String name, int code);

void listen(EventHandler onEvent) {}

Enabling this rule

This rule is in the pedantic preset, so it is enabled by preset: pedantic or by name:

many_lints.yaml

rules:
  prefer_typedefs_for_callbacks:
    enabled: true

Options

analysis_options.yaml

analysis_options.yaml

many_lints:
  rules:
    prefer_typedefs_for_callbacks:
      min_parameters: 2

many_lints.yaml

many_lints.yaml

rules:
  prefer_typedefs_for_callbacks:
    min_parameters: 2

Option	Type	Default	Description
min_parameters	int	2	How many parameters an inline function type may have

Turning this rule off

To disable this rule:

many_lints.yaml

rules:
  prefer_typedefs_for_callbacks: false

To keep the rule on but skip certain paths, use per-rule exclude.

Related rules

• prefer_explicit_function_type — Prefer explicit function type annotations over the bare ‘Function’ type.
• prefer_explicit_parameter_names — Name the parameters of a function type.
• prefer_void_callback — Use ‘VoidCallback’ instead of ‘void Function()’.
• prefer_async_callback — Use ‘AsyncCallback’ instead of ‘Future<void> Function()’.