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package main
import (
"fmt"
bexpr "github.com/hashicorp/go-bexpr"
)
type Internal struct {
Name string
// Use an alternative name for referencing this field in expressions
Values []int `bexpr:"fields"`
// Hides this field so it cannot be used in expression evaluation
Hidden int `bexpr:"-"`
// Unexported fields are not available for use by the evaluator
unexported int
}
type Matchable struct {
Map map[string]string
X int
Internal Internal
// Slices are handled specially. If any value within the slice
// evaluates to true the overall evaluation for the slice will
// be true.
SliceInternal []Internal
MapInternal map[string]Internal
}
var data Matchable = Matchable{
Map: map[string]string{
"abc": "def",
"ghi": "jkl",
"mno": "pqr",
"stu": "vwx",
"y": "z",
},
X: 5,
Internal: Internal{
Name: "main",
Values: []int{1, 2, 3, 4, 5},
},
SliceInternal: []Internal{
Internal{
Name: "odd",
Values: []int{1, 3, 5, 7, 9},
},
Internal{
Name: "even",
Values: []int{2, 4, 6, 8, 10},
},
Internal{
Name: "fib",
Values: []int{0, 1, 1, 2, 3, 5},
},
},
MapInternal: map[string]Internal{
"odd": Internal{
Name: "odd",
Values: []int{1, 3, 5, 7, 9},
},
"even": Internal{
Name: "even",
Values: []int{2, 4, 6, 8, 10},
},
"fib": Internal{
Name: "fib",
Values: []int{0, 1, 1, 2, 3, 5},
},
},
}
var expressions []string = []string{
// should error out in creating the evaluator as Foo is not a valid selector
"Foo == 3",
// should error out because the field is hidden
"Internal.Hidden == 5",
// should error out because the field is not exported
"Internal.unexported == 3",
// should evaluate to true
"Map[`abc`] == `def`",
// should evaluate to false
"X == 3",
// should evaluate to true
"Internal.fields is not empty",
// should evaluate to true
"0 in SliceInternal.fields",
// should evaluate to false
"4 not in SliceInternal.fields",
// should evaluate to false
"MapInternal.fib.Name != fib",
// should evaluate to true
"odd in MapInternal",
}
func main() {
for _, expression := range expressions {
eval, err := bexpr.CreateEvaluatorForType(expression, nil, (*Matchable)(nil))
if err != nil {
fmt.Printf("Failed to create evaluator for expression %q: %v\n", expression, err)
continue
}
result, err := eval.Evaluate(data)
if err != nil {
fmt.Printf("Failed to run evaluation of expression %q: %v\n", expression, err)
continue
}
fmt.Printf("Result of expression %q evaluation: %t\n", expression, result)
}
}
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