A QML implementation of the SuperAgent HTTP client.

version 1.5.0

To install:

❯ qpm install com.cutehacks.duperagent

Build Status

DuperAgent is a QML clone of the fantastic SuperAgent library from VisionMedia.

The library is implemented in Qt/C++ and designed as an alternative to QML's builtin implementation of XmlHttpRequest.


  • Modern API in comparison to XmlHttpRequest
  • Support for multipart/form uploads
  • Automatic parsing of response bodies with known content-types
  • Built-in persistent cookie jar
  • Promise API
  • Secure connection (SSL/TLS) API
  • Network activity indicator
  • Image utilities


  • DuperAgent requires Qt 5.4.
  • DuperAgent does not implement the XML API of XmlHttpRequest

Migration from v0.x.x to v1.x.x

There have been no API removals in the 1.x release so code written using v0.x should continue to work without modification.

There is however one major behavioral change. v1.x enables a cookie jar by default such that responses containing cookies will send those cookies with applicable requests. This may introduce a security issue for some applications, so to disable this behavior and revert to v0.x behavior, call this function somewhere during initialization before making any requests:

        cookieJar: false


With qpm

Duperagent is available on and can easily be installed like so:

qpm install com.cutehacks.duperagent

Adding the following line to your .pro file will pull in all of your qpm dependencies, including DuperAgent.


Without qpm

Alternatively you can clone the repository directly and include it in your project:



Once the files are compiled into your binary, DuperAgent will register it's types with the QMLEngine automatically. Import the module and start using it inside your .qml files:

import com.cutehacks.duperagent 1.0 as Http


        .end(function(err, res) {
            console.log(JSON.stringify(res.header, null, 4));
            console.log(JSON.stringify(res.body, null, 4));

You can of course use whatever you want instead of Http, but this documentation uses this alias throughout.

Request API

At this point in time, the API should be almost identical to that of SuperAgent so that documentation is recommended. The following functions are not yet implemented in DuperAgent:

  • withCredentials: CORS - Not implemented
  • buffer: Response body buffering is not yet implemented
  • pipe: Piping to streams is not supported

That being said, the following API additions are also available:


A function for setting global configuration options for the agent. This function should be called once before any requests are made. It is good practice to call this from a Component.onCompleted signal. For example:

    Component.onCompleted: {
            cache: false

The following is a list of supported configuration options:


This option controls the cache behavior of the agent. The default is to create a QNetworkDiskCache with a sensible path for the platform. If you wish to disable this behavior, for example because you have your own cache, you can set this property to false. The property can be further customized by passing an object.

        cache: {
            maxSize: 20000,
            location: "/path/to/cache"
  • maxSize: The maximum size of the cache
  • location: The full path to the directory for caching files. The default is <CacheLocation>/duperagent


This option controls the cookie jar of the agent. The default is to create an instance of a QNetworkCookieJar that additionally persists the cookies to disk. If you wish to disable this behavior, for example because you have your own cookie jar, you can set this property to false. This property can be further customized by passing an object.

        cookieJar: {
            location: "/path/to/cookies.txt"
  • location: The full path to the file to use for the disk storage. The default is <AppDataLocation>/duperagent_cookies.txt


This option controls the proxy settings used by agent. By default Qt does not use a proxy, however you can use the system proxy by setting this value to "system".

        proxy: "system"


This function behaves similar to document.cookie as implemented in browsers.

Calling the property as a getter will return all cookies in the cookie jar as a semi-colon separated string. Note that this function will not return cookies that are marked as HttpOnly.

Calling the property as a setter will add the cookie to the cookie jar. If there is an existing cookie with the same identifying tuple in the jar, it will overwrite it. Note that it is not possible to overwrite cookies marked as HttpOnly. Attempts to overwrite these will be silently ignored.


This function will clear all saved cookies including those marked as HttpOnly.


This function is set to override the cache save behavior for a single request. Setting it to true will enable caching, while false implies the response will not be cached.

      .end(function(err, res) {
        // ...


This function is set to override the cache behavior for a single request. It can have the following values:

  • Http.CacheControl.AlwaysNetwork
  • Http.CacheControl.PreferNetwork (default)
  • Http.CacheControl.PreferCache
  • Http.CacheControl.AlwaysCache
      .end(function(err, res) {
        // ...

Promise API

This package contains an implementation of the Promises/A+ specification and also offers an API similar to the Promises API in ES2017. For more information, please see MDN

At some point this API may be split out into it's own module.


Creates a new Promise object.

Since the Javascript engine in QML does not allow us to expose new types with constructors, the new Promise(executor) syntax is not supported. Instead the create function can be used like so:

var p = Http.Promise.create(function(resolve, reject) {

    asynchronousStuff(function(success) {
        if (success) {
        } else {
            reject("something failed");


p1.then(function(value) {
    // success
}).catch(function(reason) {
    // failure


Returns a resolved promise.

var p = Http.Promise.resolve(5);

p.then(function(value) {
    console.log(value); // 5


Returns a rejected promise.

var p = Http.Promise.reject("error");

p.catch(function(reason) {
    console.log(reason); // "error"


Concurrently executes several promises and returns another promise that is fulfilled when the original promises are fulfilled. The resolved value is an array containing the values of the original promises in the original order (not the order they were fulfilled).

If one of the original promises fail, the returned promise will be rejected with the same reason.

var p1 = Http.Promise.resolve(3);
var p2 = 1337;
var p3 = Http.Request
        .then(function(resp) {
            return resp.body;

var p4 = Http.Promise.all([p1, p2, p3]);

p4.then(function(values) {
    console.log(values[0]); // 3
    console.log(values[1]); // 1337
    console.log(values[2]); // resp.body


Concurrently executes several promises and returns another promise that is fulfilled when the first of those promises is fulfilled.

var p1 = Http.Request
     .then(function(resp) {
         return 3;

var p2 = Http.Request
    .then(function(resp) {
        return 1;

var p3 = Http.Promise.race([p1, p2]);

p3.then(function(value) {
    console.log(value); // 1

NetworkActivityIndicator API

The network activity indicator item exposes properties that can be used to show when there are outstanding network requests in the application. There is a native implementation for iOS and there is also a generic implementation that works on all platforms (including iOS).

Only network request created through Duperagent are considered.

enabled : bool

A read-only property that is true when Duperagent has a non-zero number of pending network requests. It can be used to show a busy indicator or some other visual element to indicate that something is happening.

activationDelay : int

Time (in ms) to wait before enabling the network activity indicator after new requests have been initiated. The default is 1000 ms.

completionDelay : int

Time (in ms) to wait before disabling the network activity indicator after all requests have completed. The default is 170 ms.

enableNativeIndicator : bool

A property that indicates if the native implementation of a network activity indicator should be used. This feature is only available on iOS. The default value of this property is false.

ImageUtils API

The ImageUtils module provides functionality for scaling and cropping an image file before uploading it via DuperAgent's attach function. The first step is to create a reader and then get and set properties on the reader before calling read to load the image with the given settings.


This function accepts a file path to an image or to a base64 encoded data uri containing image data and returns an image reader. The image is not decoded at this point, only the reader is created.


Returns an object with the width and height properties of the image without actually decoding the image.


Returns the filesize (in bytes) of the encoded image.


Sets the desired scaled size for the image when it is decoded. Depending on the image format, some decoders can do this efficiently without having to decode the full image first and then downscale.

var reader = Http.ImageUtils.createReader(imagePath);
reader.setScaledSize(200, 200, Image.PreserveAspectCrop);;

NOTE: Only the first 3 enumerations of Image.fitMode are supported in the final (optional) argument to the function. If the third argument is omitted, it defaults to Image.Stretch.


Sets the clip rect for image reader.

var reader = Http.ImageUtils.createReader(imagePath);
reader.setClipRect(0, 0, 200, 200);;

See also QImageReader::setClipRect.


Sets a scaled clip rect for image reader.

var reader = Http.ImageUtils.createReader(imagePath);
reader.setScaledClipRect(0, 0, 200, 200);;

See also QImageReader::setScaledClipRect.


Rotates the image if the metadata for the image indicates that it should.

    .setScaledSize(200, 200)

NOTE: This function has no effect on versions of Qt prior to Qt 5.5.0.


The function that actually reads and decodes the image into memory based on the settings previously configured on the reader. This function takes an optional object of options which can transcode the image to a different format and quality.

    .setScaledSize(200, 200)
        transcode: {
            format: "jpg",
            quality: 50

The object returned from this function can be passed to the attach function of the request type as the second argument.


Jason Barron

View on Github

License: MIT

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