英文:
Concise way to do multiple interface conversions in Golang?
问题
我正在尝试使用go/ast包从代码中解析函数调用。
为了做到这一点，我首先找到所有的函数调用，如下所示：
ast.Inspect(f, func(n ast.Node) bool {switch x := n.(type) {case *ast.FuncDecl:processFunction(x)}return true})
然后，processFunction()函数如下所示：
func processFunction(e *ast.FuncDecl) {// 保存包装函数名f := e.Name.Namefor _, expression := range e.Body.List {logrus.Printf("Current stmt: %#v", expression)pkg := expression.(*ast.ExprStmt).X.(*ast.CallExpr).Fun.(*ast.SelectorExpr).X.(*ast.Ident).Namefn := expression.(*ast.ExprStmt).X.(*ast.CallExpr).Fun.(*ast.SelectorExpr).Sel.Namefcall := fmt.Sprintf("%s.%s", pkg, fn)logrus.Printf("Yay. found my function call: ", fcall)}}
这段代码的问题在于，如果在AST中找不到特定的层次结构，程序会发生崩溃。我知道我们可以通过以下方式优雅地进行接口转换：
x, ok := x.(type)
但是，如果我对每个转换都这样做，我的代码会变得很冗长。当然，在这里尝试使用这种方法会失败。
pkg, ok := expression.(*ast.ExprStmt).X.(*ast.CallExpr).Fun.(*ast.SelectorExpr).X.(*ast.Ident).Nameif !ok {continue}
错误信息：
./parser.go:41: assignment count mismatch: 2 = 1
有没有一种简洁的方法来进行这些连续的转换，并且在找不到这个层次结构时能够优雅地处理错误？
英文:
I'm trying to parse function calls from a code using go/ast package.
To do that, I first find all function calls like:
ast.Inspect(f, func(n ast.Node) bool {switch x := n.(type) {case *ast.FuncDecl:processFunction(x)}return true})
And then, processFunction() looks like this:
func processFunction(e *ast.FuncDecl) {// Save wrapper function namef := e.Name.Namefor _, expression := range e.Body.List {logrus.Printf("Current stmt: %#v", expression)pkg := expression.(*ast.ExprStmt).X.(*ast.CallExpr).Fun.(*ast.SelectorExpr).X.(*ast.Ident).Namefn := expression.(*ast.ExprStmt).X.(*ast.CallExpr).Fun.(*ast.SelectorExpr).Sel.Namefcall := fmt.Sprintf("%s.%s", pkg, fn)logrus.Printf("Yay. found my function call: ", fcall)}}
The problem with this code is that if that particular hierarchy is not found in AST, the program panics. I know that we can do interface conversions gracefully via
x, ok := x.(type)
But, if I do each conversion like this, my code will be huge. Trying to use that in this fails of course.
pkg, ok := expression.(*ast.ExprStmt).X.(*ast.CallExpr).Fun.(*ast.SelectorExpr).X.(*ast.Ident).Nameif !ok {continue}
Error:
./parser.go:41: assignment count mismatch: 2 = 1
Is there a concise way to do these series of conversions and also fail gracefully if this hierarchy is not found?
答案1
得分: 1
我已经为您翻译了代码部分，如下所示：
// 无法使用*类型断言*来链接。但是，您可以通过将重复的代码提取到自己的函数中来简化此特定示例。func fnSelExpr(s ast.Stmt) (*ast.SelectorExpr, bool) {if xs, ok := s.(*ast.ExprStmt); ok {if cx, ok := xs.X.(*ast.CallExpr); ok {return cx.Fun.(*ast.SelectorExpr)}}return nil, false}然后，您可以像这样简化您的`processFunction`函数。func processFunction(e *ast.FuncDecl) {// 保存包装函数名称f := e.Name.Namefor _, expression := range e.Body.List {logrus.Printf("当前语句: %#v", expression)sx, ok := fnSelExpr(expression)if !ok {continue}var pkg stringif id, ok := sx.X.(*ast.Ident); ok {pkg = id.Name}fn := sx.Sel.Namefcall := fmt.Sprintf("%s.%s", pkg, fn)logrus.Printf("耶。找到了我的函数调用: ", fcall)}}
希望对您有所帮助！
英文:
There is no way, that I know of, to chain type assertions. But you can simplify this specific example by extracting duplicate code into its own function.
func fnSelExpr(s ast.Stmt) (*ast.SelectorExpr, bool) {if xs, ok := s.(*ast.ExprStmt); ok {if cx, ok := xs.X.(*ast.CallExpr); ok {return cx.Fun.(*ast.SelectorExpr)}}return nil, false}
Then you can simplify your processFunction like this.
func processFunction(e *ast.FuncDecl) {// Save wrapper function namef := e.Name.Namefor _, expression := range e.Body.List {logrus.Printf("Current stmt: %#v", expression)sx, ok := fnSelExpr(expression)if !ok {continue}var pkg stringif id, ok := sx.X.(*ast.Ident); ok {pkg = id.Name}fn := sx.Sel.Namefcall := fmt.Sprintf("%s.%s", pkg, fn)logrus.Printf("Yay. found my function call: ", fcall)}}
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