| // Copyright 2020 Google LLC |
| // |
| // Licensed under the Apache License, Version 2.0 (the "License"); |
| // you may not use this file except in compliance with the License. |
| // You may obtain a copy of the License at |
| // |
| // http://www.apache.org/licenses/LICENSE-2.0 |
| // |
| // Unless required by applicable law or agreed to in writing, software |
| // distributed under the License is distributed on an "AS IS" BASIS, |
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| // See the License for the specific language governing permissions and |
| // limitations under the License. |
| |
| package examples |
| |
| import ( |
| "fmt" |
| "log" |
| |
| "github.com/google/cel-go/cel" |
| "github.com/google/cel-go/checker/decls" |
| "github.com/google/cel-go/common/types" |
| "github.com/google/cel-go/common/types/ref" |
| "github.com/google/cel-go/interpreter/functions" |
| |
| exprpb "google.golang.org/genproto/googleapis/api/expr/v1alpha1" |
| ) |
| |
| func ExampleCustomInstanceFunction() { |
| env, err := cel.NewEnv(cel.Lib(customLib{})) |
| if err != nil { |
| log.Fatalf("environment creation error: %v\n", err) |
| } |
| // Check iss for error in both Parse and Check. |
| ast, iss := env.Compile(`i.greet(you)`) |
| if iss.Err() != nil { |
| log.Fatalln(iss.Err()) |
| } |
| prg, err := env.Program(ast) |
| if err != nil { |
| log.Fatalf("Program creation error: %v\n", err) |
| } |
| |
| out, _, err := prg.Eval(map[string]interface{}{ |
| "i": "CEL", |
| "you": "world", |
| }) |
| if err != nil { |
| log.Fatalf("Evaluation error: %v\n", err) |
| } |
| |
| fmt.Println(out) |
| // Output:Hello world! Nice to meet you, I'm CEL. |
| } |
| |
| type customLib struct{} |
| |
| func (customLib) CompileOptions() []cel.EnvOption { |
| return []cel.EnvOption{ |
| cel.Declarations( |
| decls.NewIdent("i", decls.String, nil), |
| decls.NewIdent("you", decls.String, nil), |
| decls.NewFunction("greet", |
| decls.NewInstanceOverload("string_greet_string", |
| []*exprpb.Type{decls.String, decls.String}, |
| decls.String))), |
| } |
| } |
| |
| func (customLib) ProgramOptions() []cel.ProgramOption { |
| return []cel.ProgramOption{ |
| cel.Functions( |
| &functions.Overload{ |
| Operator: "string_greet_string", |
| Binary: func(lhs ref.Val, rhs ref.Val) ref.Val { |
| return types.String( |
| fmt.Sprintf("Hello %s! Nice to meet you, I'm %s.\n", rhs, lhs)) |
| }, |
| }, |
| ), |
| } |
| } |