Monthly Archives: June 2015

Developing a FileSystemWatcher for OS X by using FSEvents with Swift 2.0

When Swift was announced at WWDC 2014, I was very disappointed to not be able to use some of powerful C APIs such as FSEvents, to write applications in pure Swift language.

A lot of C APIs needs a C function pointer to pass a callback function when you use the API. From Swift 1.0 to Swift 1.2, it was not possible to use C function pointer in pure Swift language.

It was possible to use FSEvents by wrapping it in an Objective-C class, and by calling this class in Swift by using the bridging features offered by the language, but it was not what I attempted to accomplish.

But things change and at WWDC 2015, Apple announced the possibility to use C function pointers with Swift 2.0.

Today I’m very pleased to give you a sample code which is a good starting point to create your own FileSystemWatcher using the FSEvents API written with Swift 2.0.

import Foundation

public class FileSystemWatcher {

    // MARK: - Initialization / Deinitialization
    public init(pathsToWatch: [String], sinceWhen: FSEventStreamEventId) {
        self.lastEventId = sinceWhen
        self.pathsToWatch = pathsToWatch

    convenience public init(pathsToWatch: [String]) {
        self.init(pathsToWatch: pathsToWatch, sinceWhen: FSEventStreamEventId(kFSEventStreamEventIdSinceNow))
    deinit {

    // MARK: - Private Properties
    private let eventCallback: FSEventStreamCallback = { (stream: ConstFSEventStreamRef, contextInfo: UnsafeMutablePointer<Void>, numEvents: Int, eventPaths: UnsafeMutablePointer<Void>, eventFlags: UnsafePointer<FSEventStreamEventFlags>, eventIds: UnsafePointer<FSEventStreamEventId>) in
        print("***** FSEventCallback Fired *****", appendNewline: true)
        let fileSystemWatcher: FileSystemWatcher = unsafeBitCast(contextInfo, FileSystemWatcher.self)
        let paths = unsafeBitCast(eventPaths, NSArray.self) as! [String]
        for index in 0..<numEvents {
            fileSystemWatcher.processEvent(eventIds[index], eventPath: paths[index], eventFlags: eventFlags[index])
        fileSystemWatcher.lastEventId = eventIds[numEvents - 1]
    private let pathsToWatch: [String]
    private var started = false
    private var streamRef: FSEventStreamRef!
    // MARK: - Private Methods
    private func processEvent(eventId: FSEventStreamEventId, eventPath: String, eventFlags: FSEventStreamEventFlags) {
        print("\t\(eventId) - \(eventFlags) - \(eventPath)", appendNewline: true)
    // MARK: - Pubic Properties
    public private(set) var lastEventId: FSEventStreamEventId
    // MARK: - Pubic Methods
    public func start() {
        guard started == false else { return }
        var context = FSEventStreamContext(version: 0, info: nil, retain: nil, release: nil, copyDescription: nil) = UnsafeMutablePointer<Void>(unsafeAddressOf(self))
        let flags = UInt32(kFSEventStreamCreateFlagUseCFTypes | kFSEventStreamCreateFlagFileEvents)
        streamRef = FSEventStreamCreate(kCFAllocatorDefault, eventCallback, &context, pathsToWatch, lastEventId, 0, flags)
        FSEventStreamScheduleWithRunLoop(streamRef, CFRunLoopGetMain(), kCFRunLoopDefaultMode)
        started = true
    public func stop() {
        guard started == true else { return }

        streamRef = nil

        started = false

I hope this will help you in your future applications and feel free to share this article if you found it helpful 😉

Developing Yammer apps for iOS/OS X with ADAL, REST API and Swift 2.0

You’re interested to develop applications on top of Yammer (Microsoft’s Enterprise Social Network) but you’re currently working on iOS/OS X devices ? No problem 😉

Yammer offer to developers a REST API to allow them build applications on top of the product. Microsoft has also started to move the authentication mechanism to Office 365, to let people to use the same credentials as for other services in their company (Outlook, SharePoint, Skype for Business…).

In this article, we’ll discover what are the main steps to create our first application which will use the Yammer REST API and Office 365 authentication, in conjunction with Swift 2.0, the new programming language of Apple platforms, updated during the WWDC 2015.

Declare your application in Azure Active Directory

The first step to accomplish to be able to develop an application which will call the Yammer REST API with the Office 365 authentication (based on Azure AD), is to declare your application in Azure.

To do this, you need to be a global administrator of your tenant, and you can achieve this by using the Azure Management Portal :

On the Azure Management Portal, go to Active Directory section, select the appropriate directory, select applications and create a new native application.

After you fill the requested information (a name and a redirect URL), you have to declare for each service (SharePoint, Exchange, Active Directory…) what permissions are needed by your application as you can see below.

Few weeks ago, Microsoft has released a new permission which allows you to use the Yammer REST API (it’s a preview for now). So just add it to your application (as you can see below) and save your modifications.

Office 365 Yammer - Azure AD Permissions

Authenticate with ADAL

The second step to develop your application is to acquire an authentication token from Azure AD and to pass it to the Yammer REST API when you want to retrieve data.

The simplest way to acquire an authentication token from Azure AD is to use the Azure Active Directory Library (aka. ADAL) which can be downloaded for free on GitHub :

After downloading the library and integrating it in your application (cf. documentation on GitHub on how to achieve this goal), you can acquire a token with just few lines of code.

var authError: ADAuthenticationError?
var authContext = ADAuthenticationContext(authority: "", error: &authError)
var bearerToken: String!

authContext.acquireTokenWithResource("", clientId: "...", redirectUri: "...", completionBlock: { (result: ADAuthenticationResult!) in
    guard (authError == nil) && (result.accessToken != nil) else {
        // Authentication Error

    bearerToken = result.accessToken

The Swift code above is pretty simple to understand :

  • We declare an authentication context
  • We call the acquireTokenWithResource method with required parameters (clientId and redirectUri are the same you filled in step #1)
  • If the token was successfully acquired, we store it in a variable to use it later

Use the Yammer REST API

Now that we have a valid authentication token, we are now able to use the Yammer REST API. If you need some information about all the capabilities available in that API, you can refer to the official documentation :

In Swift, we are able to use all the frameworks (Foundation, AppKit, UIKit…) available on iOS/OS X and which allow us to perform advanced operations in a simple manner.

To perform HTTP communications, we can use the NSURLSession class. With just few lines of code, we are able to send a request to a server (synchronously or asynchronously) and to retrieve the response.

let URLSession = NSURLSession(configuration: NSURLSessionConfiguration.defaultSessionConfiguration())
let request = NSMutableURLRequest(URL: NSURL(string: "")!)
request.setValue("application/json", forHTTPHeaderField: "Accept")
request.setValue(bearerToken, forHTTPHeaderField: "Auhtorization")
let task = URLSession.dataTaskWithRequest(request) { (data: NSData?, response: NSURLResponse?, error: NSError?) in
    guard (data != nil) else {
        // No data returned

The most important part in the code above, to authenticate the request, concerns the addition of an Authorization header to the request. The header is a concatenation of the token retrieved in step 2 with the Bearer keyword such as “Authorization: Bearer our_authentication_token“.

If the request is successfully executed (it returns data), then we call the processResult method by passing the retrieved data as parameter.

Deserialize JSON response and catch errors

The last step to perform in our application is to parse the retrieved data. Because we have passed an Accept header to the previous request to indicate that we want to retrieve the data as JSON, we just have to deserialize and to use them.

Once again thanks to Foundation which expose a class (NSJSONSerialization) to perform this operation.

If you used Swift 1.x during the last year, focus your attention on the code below. A brand new way to deserialize and catch potential errors has been introduced with Swift 2.0 (do … catch).

func processResult(data: NSData?) {    
    do {
        let JSONObject = try NSJSONSerialization.JSONObjectWithData(data!, options: [])
        print(JSONObject, appendNewline: true)
    } catch let error as NSError {
        print(error, appendNewline: true)

In the code above, we just print the deserialize object so it should display something like that :

    "activated_at" = "2015/01/01 01:01:00 +0000";
    admin = true;
    "birth_date" = "";
    "can_broadcast" = true;
    "can_browse_external_networks" = 1;
    "can_create_new_network" = 1;
    contact = { ... };
    department = Direction;
    email = "...";
    expertise = "Office 365 REST API, SharePoint, iOS, Objective-C, Swift";
    "external_urls" = ();
    "first_name" = "Stéphane";
    "follow_general_messages" = 0;
    "full_name" = "Stéphane Cordonnier";
    guid = "<null>";
    id = 123456789;
    interests = "<null>";
    "job_title" = "Technology Addict";
    "kids_names" = "<null>";
    "last_name" = Cordonnier;
    location = Paris;

If you want to use and parse the deserialized object, it’s a key/value dictionary so it’s pretty simple to use it.

Search videos using the Office 365 Video REST API

Office 365 is an awesome solution to share videos in a dedicated portal, organized in different channels. Channels are used (for example) to split videos by themes or categories.

But if you create a lot of channels in your organization or if you have a lot of videos in each channel, it may be pretty difficult to find relevant videos.

If you want to create an application on top of Office 365 Video, it’s interesting to know that the REST API exposes capabilities to search videos, globally at the service level, or at the channel level.

Build and submit search queries

When you want to use the Office 365 Video REST API, you have to submit requests to the endpoint which is only accessible through the portal URL as you can see below.

As we previously said, this endpoint exposes search capabilities at two different levels :

  • Video Service (across all channels)
  • Channel

Depending on which level you want to search videos, you have to build requests by appending path components as you can see below :

Across all channels

On a specific channel'01234567-abcd-cded-1234-1234567890ab')/Search/Query

Add parameters to the querystring to specify search criterias

To retrieve only information that you want, you have to add some parameters to the querystring. Three possibilites are offered to you :

  • querytext
  • startItemIndex
  • itemLimit

As you can imagine, the most important parameter is querytext which allows you to make fulltext searches. startItemIndex and itemLimit are used to perform paging operations.

For example if you want to search the first 10 videos which contains the ‘Awesome’ word, across all channels, your request should look something like that :'Awesome'&itemLimit=10

In the same manner, if you want to retrieve the same videos on a specific channel, your query should look something like that :'01234567-abcd-cded-1234-1234567890ab')/Search/Query?querytext='Awesome'&itemLimit=10

By querying those URLs, you will retrieve a list of videos. Each video is described by the following structure :

<category term="SP.Publishing.VideoItem" scheme="" />
<link rel="edit" href="VideoService/Channels(guid'01234567-abcd-cded-1234-1234567890ab')/Videos(guid'01234567-abcd-cded-1234-1234567890ab')" />
<link rel="" type="application/atom+xml;type=entry" title="Author" href="VideoService/Channels(guid'01234567-abcd-cded-1234-1234567890ab')/Videos(guid'01234567-abcd-cded-1234-1234567890ab')/Author" />
<link rel="" type="application/atom+xml;type=entry" title="Owner" href="VideoService/Channels(guid'01234567-abcd-cded-1234-1234567890ab')/Videos(guid'01234567-abcd-cded-1234-1234567890ab')/Owner" />
<link rel="" type="application/atom+xml;type=feed" title="PeopleInMedia" href="VideoService/Channels(guid'01234567-abcd-cded-1234-1234567890ab')/Videos(guid'01234567-abcd-cded-1234-1234567890ab')/PeopleInMedia" />
<title />
  <name />
<content type="application/xml">
    <d:ChannelID m:type="Edm.Guid">01234567-abcd-cded-1234-1234567890ab</d:ChannelID>
    <d:CreatedDate m:type="Edm.DateTime">2015-01-01T01:00:00Z</d:CreatedDate>
    <d:Description />
    <d:OwnerName>Stephane Cordonnier</d:OwnerName>
    <d:Title>My Awesome Video</d:Title>
    <d:ID m:type="Edm.Guid">01234567-abcd-cded-1234-1234567890ab</d:ID>
    <d:VideoDurationInSeconds m:type="Edm.Int32">120</d:VideoDurationInSeconds>
    <d:VideoProcessingStatus m:type="Edm.Int32">2</d:VideoProcessingStatus>
    <d:ViewCount m:type="Edm.Int32">10</d:ViewCount>

Retrieve popular videos across all channels, or for a specific channel

It’s great to be able to search for videos but if you use the web version of Office 365 Video, you probably saw that the homepage displays popular videos. I guess you wonder how to retrieve those videos ?

The search endpoint mentioned above has special syntax to get those data. If you want to retrieve popular videos globally or for a specific channel, you have to submit requests using the following URLs:'01234567-abcd-cded-1234-1234567890ab')/Search/Popular

As for simple searches, you can use startItemIndex and itemLimit to perform paging through popular videos.

If you want more information on the Office 365 Video REST API, you can read the official documentation on the MSDN website :

AADSTS90093 – Calling principal cannot consent due to lack of permissions

When you develop your own applications which use the Office 365 REST API, it might happen that users are facing the following error message when they try to authenticate, when your application is supposed to ask the consent of the user to access his data.

AADSTS90093 - Authentication Error

The difficult thing to understand is why this message is displayed and why all users are not concerned ?

Declare the application’s rights in Azure AD

When you create an application, you have to declare which rights are needed to access data when you make calls to the REST API.

Those rights are declared in Azure AD through the web console ( as you can see below.

Azure Manage Portal - Application Permissions

Which is not indicated in the web console is that some of those rights need that an administrator (at the tenant level) give a consent to allow your application to use them.

If the consent of an administrator was not given and a non-administrator user tries to use the application, he will receive the following error message : AADSTS90093 – Calling principal cannot consent due to lack of permissions.

What permissions require an administrator consent ?

If you would like a complete description of how permissions work on Office 365, you could refer to the official documentation on MSDN :

In short if you want to know what permissions require an administrator consent, it depends of which product  and which features you want to use.

You can find below a quick summary (grouped by products) of all the permissions which require an administrator consent. All other permissions (not listed below) only require a user consent.


  • Have full control of all site collections
  • Run search queries as a user
  • Read user profiles
  • Read and write user profiles
  • Read managed metadata
  • Read and write managed metadata


No permission requires an administrator consent

Azure Active Directory

  • Read all users’ full profiles
  • Read directory data (except if the application is registered in the same tenant as the user)
  • Read and write directory data
  • Access the directory as the signed-in user (only for web applications)


No permission requires an administrator consent

What to do if I encounter the error message ?

If you are facing to the error message mentioned previously, the first thing to do is to check if your application uses one of the permission in the list above.

If it’s the case, make sure that you absolutely need it, otherwise remove the right from the declared permissions for your application in Azure AD and it should solve the problem.

For example, you can perform searches on SharePoint sites under the identity of the current user, even if you only have the “Read items in all site collection” permission. It’s not needed to add the “Run search queries as a user” permission.

If you need the permission, you have to ask a tenant administrator to consent your application. Until the administrator consent, all users which are not administrators of the Office 365 tenant won’t be able to log-in and use your application.