cty
(pronounced "see-tie", emoji: ๐ ๐,
IPA: /si'tสฐaษช/)
is a dynamic type system for applications written
in Go that need to represent user-supplied values without losing type
information. The primary intended use is for implementing configuration
languages, but other uses may be possible too.
One could think of cty
as being the reflection API for a language that
doesn't exist, or that doesn't exist yet. It provides a set of value types
and an API for working with values of that type.
Fundamentally what cty
provides is equivalent to an interface{}
with some
dynamic type information attached, but cty
encapsulates this to ensure that
invariants are preserved and to provide a more convenient API.
As well as primitive types, basic collection types (lists, maps and sets) and
structural types (object, tuple), the cty
type and value system has some
additional, optional features that may be useful to certain applications:
-
Representation of "unknown" values, which serve as a typed placeholder for a value that has yet to be determined. This can be a useful building-block for a type checker. Unknown values support all of the same operations as known values of their type, but the result will often itself be unknown.
-
Representation of values whose types aren't even known yet. This can represent, for example, the result of a JSON-decoding function before the JSON data is known.
Along with the type system itself, a number of utility packages are provided
that build on the basics to help integrate cty
into calling applications.
For example, cty
values can be automatically converted to other types,
converted to and from native Go data structures, or serialized as JSON.
For more details, see the following documentation:
- Concepts
- Full Description of the
cty
Types - API Reference (godoc)
- Conversion between
cty
types - Conversion to and from native Go values
- JSON serialization
cty
Functions system
Copyright 2017 Martin Atkins
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