nodefault

Documentation

Overview

Package nodefault provides newtypes around builtin Go types so that if the newtype is used as a field in a struct and that field is zero-initialized (https://golang.org/ref/spec#The_zero_value), accessing the field will cause a null pointer deref panic. Or in other terms: It soft-enforces that the caller sets the field explicitly when constructing the struct.

Example:

type Config struct {
    // This field must be set to a non-nil value,
    // forcing the caller to make their mind up
    // about this field.
    CriticalSetting   *nodefault.Bool
}

An function that takes such a Config should _not_ check for nil-ness: and instead unconditionally dereference:

func f(c Config) {
    if (c.CriticalSetting) { }
}

If the caller of f forgot to specify the .CriticalSetting field, the Go runtime will issue a nil-pointer deref panic and it'll be clear that the caller did not read the docs of Config.

f(Config{}) // crashes

f Config{ CriticalSetting: &nodefault.Bool{B: false}} // doesn't crash

Index

• type Bool
  • func (n *Bool) String() string
  • func (n *Bool) ValidateNoDefault() error

Types

type Bool

type Bool struct{ B bool }

func (*Bool) String

func (n *Bool) String() string

func (*Bool) ValidateNoDefault

func (n *Bool) ValidateNoDefault() error