mirror of
https://github.com/letic/terraform-provider-google.git
synced 2024-09-07 09:36:44 +00:00
72 lines
3.0 KiB
Go
72 lines
3.0 KiB
Go
![]() |
package cty
|
||
|
|
||
|
// Value represents a value of a particular type, and is the interface by
|
||
|
// which operations are executed on typed values.
|
||
|
//
|
||
|
// Value has two different classes of method. Operation methods stay entirely
|
||
|
// within the type system (methods accept and return Value instances) and
|
||
|
// are intended for use in implementing a language in terms of cty, while
|
||
|
// integration methods either enter or leave the type system, working with
|
||
|
// native Go values. Operation methods are guaranteed to support all of the
|
||
|
// expected short-circuit behavior for unknown and dynamic values, while
|
||
|
// integration methods may not.
|
||
|
//
|
||
|
// The philosophy for the operations API is that it's the caller's
|
||
|
// responsibility to ensure that the given types and values satisfy the
|
||
|
// specified invariants during a separate type check, so that the caller is
|
||
|
// able to return errors to its user from the application's own perspective.
|
||
|
//
|
||
|
// Consequently the design of these methods assumes such checks have already
|
||
|
// been done and panics if any invariants turn out not to be satisfied. These
|
||
|
// panic errors are not intended to be handled, but rather indicate a bug in
|
||
|
// the calling application that should be fixed with more checks prior to
|
||
|
// executing operations.
|
||
|
//
|
||
|
// A related consequence of this philosophy is that no automatic type
|
||
|
// conversions are done. If a method specifies that its argument must be
|
||
|
// number then it's the caller's responsibility to do that conversion before
|
||
|
// the call, thus allowing the application to have more constrained conversion
|
||
|
// rules than are offered by the built-in converter where necessary.
|
||
|
type Value struct {
|
||
|
ty Type
|
||
|
v interface{}
|
||
|
}
|
||
|
|
||
|
// Type returns the type of the value.
|
||
|
func (val Value) Type() Type {
|
||
|
return val.ty
|
||
|
}
|
||
|
|
||
|
// IsKnown returns true if the value is known. That is, if it is not
|
||
|
// the result of the unknown value constructor Unknown(...), and is not
|
||
|
// the result of an operation on another unknown value.
|
||
|
//
|
||
|
// Unknown values are only produced either directly or as a result of
|
||
|
// operating on other unknown values, and so an application that never
|
||
|
// introduces Unknown values can be guaranteed to never receive any either.
|
||
|
func (val Value) IsKnown() bool {
|
||
|
return val.v != unknown
|
||
|
}
|
||
|
|
||
|
// IsNull returns true if the value is null. Values of any type can be
|
||
|
// null, but any operations on a null value will panic. No operation ever
|
||
|
// produces null, so an application that never introduces Null values can
|
||
|
// be guaranteed to never receive any either.
|
||
|
func (val Value) IsNull() bool {
|
||
|
return val.v == nil
|
||
|
}
|
||
|
|
||
|
// NilVal is an invalid Value that can be used as a placeholder when returning
|
||
|
// with an error from a function that returns (Value, error).
|
||
|
//
|
||
|
// NilVal is *not* a valid error and so no operations may be performed on it.
|
||
|
// Any attempt to use it will result in a panic.
|
||
|
//
|
||
|
// This should not be confused with the idea of a Null value, as returned by
|
||
|
// NullVal. NilVal is a nil within the *Go* type system, and is invalid in
|
||
|
// the cty type system. Null values *do* exist in the cty type system.
|
||
|
var NilVal = Value{
|
||
|
ty: Type{typeImpl: nil},
|
||
|
v: nil,
|
||
|
}
|