interface-name-prefix.md

Require that interface names be prefixed with I (interface-name-prefix)

Interfaces often represent important software contracts, so it can be helpful to prefix their names with I. The unprefixed name is then available for a class that provides a standard implementation of the interface.

Rule Details

This rule enforces whether or not the I prefix is required for interface names.

Options

This rule has a string option.

• "never" (default) disallows all interfaces being prefixed with "I" (or "_I")
• "always" requires all interfaces be prefixed with "I" (or "_I")

The _ prefix is sometimes used to designate a private declaration, in which case a private interface might be named _IAnimal instead of IAnimal. The rule recognizes both forms.

never

TypeScript suggests never prefixing interfaces with "I".

The following patterns are considered warnings:

interface IAnimal {
  name: string;
}

interface _IAnimal {
  name: string;
}

interface IIguana {
  name: string;
}

The following patterns are not warnings:

interface Animal {
  name: string;
}

interface Iguana {
  name: string;
}

always

The following patterns are considered warnings:

interface Animal {
  name: string;
}

interface Iguana {
  name: string;
}

The following patterns are not warnings:

interface IAnimal {
  name: string;
}

interface _IAnimal {
  name: string;
}

interface IIguana {
  name: string;
}

When Not To Use It

If you do not want to enforce interface name prefixing.

Further Reading

TypeScript Interfaces

Compatibility

TSLint: interface-name