80 lines
2.9 KiB
Go
80 lines
2.9 KiB
Go
package main
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import (
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"encoding/json"
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"errors"
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"github.com/julienschmidt/httprouter"
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"net/http"
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"strconv"
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)
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/*
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Note: The readIDParam() method doesn't use any dependencies from our
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application struct so it could just be a regular function, rather than a method on
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application. But in general, I suggest setting up all your application-specific handlers
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and helpers so that they are methods on application. It helps maintain consistency in
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your code structure, and also future-proofs your code for when those handlers and
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helpers change later and they do need access to dependency.
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Retrieve the "id" URL parameter from the current request context, then convert it to
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an integer and return it. If the operation isn't successful, return 0 and an error.
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*/
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func (app *application) readIDParam(r *http.Request) (int64, error) {
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/*
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When httprouter is parsing a request, any interpolated URL parameters will be
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stored in the request context. We can use the ParamsFromContext() function to
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retrieve a slice containing these parameter names and values.
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*/
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params := httprouter.ParamsFromContext(r.Context())
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/*
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We can then use the ByName() method to get the value of the "id" parameter from
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the slice. In our project all movies will have a unique positive integer ID, but
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the value returned by ByName() is always a string. So we try to convert it to a
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base 10 integer (with a bit size of 64). If the parameter couldn't be converted,
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or is less than 1, we know the ID is invalid so we use the http.NotFound()
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func to return a 404 Not Found Response.
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*/
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id, err := strconv.ParseInt(params.ByName("id"), 10, 64)
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if err != nil || id < 1 {
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return 0, errors.New("invalid id parameter")
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}
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return id, nil
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}
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/*
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Define a writeJSON() helper for sending responses. This takes the destination
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http.ResponseWriter, the HTTP status code to send, the data to encode to JSON, and a
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header map containing any additional HTTP headers we want to include in the response.
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*/
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func (app *application) writeJSON(w http.ResponseWriter, status int, data any, headers http.Header) error {
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// Encode the data to JSON, returning the error if there was one.
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js, err := json.Marshal(data)
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if err != nil {
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return err
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}
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// Append a newline to make it easier to view in terminal applications.
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js = append(js, '\n')
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/*
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At this point, we know that we won't encounter any more errors before writing the
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response, so it's safe to add any headers that we want to include. We loop
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through the header map and add each header to the http.ResponseWriter header map.
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Note that it's OK if the provided header map is nil. Go doesn't throw an error
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if you try to range over (or generally, read from) a nil map.
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*/
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for key, value := range headers {
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w.Header()[key] = value
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}
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// And the "Content-Type: application/json" header, then write the status code and
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// JSON response.
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w.Header().Set("Content-Type", "application/json")
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w.WriteHeader(status)
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w.Write(js)
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return nil
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}
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