src.elv.sh@v0.21.0-dev.0.20240515223629-06979efb9a2a/pkg/eval/vars/read_only.go (about)

     1  package vars
     2  
     3  import (
     4  	"src.elv.sh/pkg/eval/errs"
     5  )
     6  
     7  type readOnly struct {
     8  	value any
     9  }
    10  
    11  // NewReadOnly creates a variable that is read-only and always returns an error
    12  // on Set.
    13  func NewReadOnly(v any) Var {
    14  	return readOnly{v}
    15  }
    16  
    17  func (rv readOnly) Set(val any) error {
    18  	return errs.SetReadOnlyVar{}
    19  }
    20  
    21  func (rv readOnly) Get() any {
    22  	return rv.value
    23  }
    24  
    25  // IsReadOnly returns whether v is a read-only variable.
    26  func IsReadOnly(v Var) bool {
    27  	switch v.(type) {
    28  	case readOnly:
    29  		return true
    30  	case roCallback:
    31  		return true
    32  	default:
    33  		return false
    34  	}
    35  }