I have a struct written in Go:

```Go
// go:generate greetings
type Lady {
 name string `greeting:"Hello  maam"`
}

// go:generate greetings
type Man {
 name string `greeting:"Hello  sir"`
}
```

How would I write `greetings.go` that would generate a method for each struct? Explain briefly first without code.
user
Certainly, here's a brief explanation:

In Go, you can create a custom generator (usually a Bash script) using the `generate` command. This generator will be executed when you run `go generate` inside your package. Here's how it typically works:

1. In your package directory, create a new file called `greetings.go`.

2. In `greetings.go`, define the generated functions. These functions can be anything - in this case, a custom `generate` function would generate methods for each struct.

3. In this `generate` function, use the `reflect` package to iterate over the types defined in your `*.go` files and extract any annotations. Here's an example:

   ```Go
   func generate(n *nn.Node) (err error) {
       // Check if we're generating for a struct
       s, ok := n.(*ast.StructType)
       if !ok {
           return fmt.Errorf("not a struct")
       }

       // Iterate over all fields in the struct
       for _, f := range s.Fields {
           // If a field has a "greeting" attribute, create a custom method
           if _, ok := f.Annotations[org.Xoo.Greeting]; ok {
               name := getFieldName(f.Type, f)
               methodName := nameWithPrefix(f.Type, "Greet")
               method := `
               func (r *` + f.Type.String() + `) ` + methodName + `() string {
                   return "Hello " + r.` + name + ` + "!" }
               func (r *` + f.Type.String() + `) Set` + methodName + `(s string) { r.` + name + ` = s }
               `
               reflect.New(rtt).Elem().FieldByName(name).SetString(s)
                   r.SetGreet(s)
             }
   }
   ```

4. Customize this `generate` function to your needs. This is a simple example and you can modify it accordingly.

5. To run the `generate` tool, use the `go generate` command. This will execute your custom tool and generate the code:

   ```sh
   go generate
   ```

Overall, this is a high-level overview of what's involved in generating code in Go. It can be tricky, but there are many excellent resources online to help you get started.
assistant
I have a struct written in Go:

```Go
// go:generate greetings
type Lady {
 name string `greeting:"Hello  maam"`
}

// go:generate greetings
type Man {
 name string `greeting:"Hello  sir"`
}
```

How would I write `greetings.go` that would generate a method for each struct? Explain briefly first without code.
user
Sure, I'd be happy to explain!

The `go:generate` directive in Go is a special comment that tells Go to run a command when the `go generate` command is used. In your case, you want to generate a method for each struct that uses the `greeting` tag.

Here's a brief explanation of how you could approach this:

1. **Parse the Go file**: You'll need to write a program that can parse the Go file and extract the structs and their fields. The `go/ast` package can be helpful for this.

2. **Identify structs with `greetings` directive**: Not all structs will have the `greetings` directive. You'll need to identify the ones that do.

3. **Extract the `greeting` tag**: For each field in the structs with the `greeting` directive, extract the `greeting` tag. The `reflect` package can be used to access struct tags.

4. **Generate the method**: For each struct, generate a method that uses the `greeting` tag to create a greeting. The method should take no arguments and return a string. The `go/format` and `os` packages can be used to write the generated code to a file.

Now, let's write the `greetings.go` file according to the steps outlined above.
assistant