structs

Overview ¶

Package structs provides small, generic helpers for working with pointers and zero values.

Despite the package name, these helpers are not limited to struct types. They are intended to reduce boilerplate around common “is this value present?” checks that appear throughout go-service configuration and wiring.

Concepts: nil, zero, and empty ¶

This package distinguishes three closely related concepts:

• nil: the pointer itself is nil (no value is present).

• zero: a non-pointer value equals its type’s zero value (for example 0 for integers, "" for strings, false for bools, an empty struct value, etc.). In this package, “zero” is determined via == comparison against the zero value of the type.

• empty: a pointer is considered “empty” when either it is nil or it points to the zero value of its element type.

Functions ¶

IsNil reports whether a pointer is nil.

IsZero reports whether a value equals the zero value for its type. Because it relies on ==, the type parameter must be comparable.

IsEmpty reports whether a pointer is nil or points to a zero value.

Examples ¶

nilPtr := (*int)(nil)
_ = structs.IsNil(nilPtr)   // true
_ = structs.IsEmpty(nilPtr) // true

v := 0
p := &v
_ = structs.IsNil(p)    // false
_ = structs.IsZero(v)   // true
_ = structs.IsEmpty(p)  // true (points to zero)

w := 42
q := &w
_ = structs.IsEmpty(q) // false

Notes and limitations ¶

• IsZero and IsEmpty require comparable element types (T comparable). If you need “zero” semantics for non-comparable types (for example slices, maps, or structs containing non-comparable fields), you must define your own notion of emptiness or use reflection-based checks (with the usual tradeoffs).

• For pointer types, IsEmpty treats “pointer to zero” as empty. This is useful for optional configuration values where a pointer may be present but carry the default/zero value and you want to treat that as “unset”. If you need to distinguish “unset (nil)” from “explicitly set to zero”, do not use IsEmpty; check nil explicitly and handle the pointed-to value separately.