Collecting data with Trackers and Webhooks

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  6. Objective-C (iOS) (0.3.0)

Objective-C (iOS) (0.3.0)

1. Overview

The Snowplow iOS Tracker allows you to track Snowplow events from your iOS apps and games. It supports iOS 7.0+.

The tracker should be straightforward to use if you are comfortable with iOS development; its API is modelled after Snowplow’s Python Tracker so any prior experience with that tracker is helpful but not necessary. If you haven’t already, have a look at the iOS Tracker Setup guide before continuing.

You can also find detailed documentation for the method calls in the tracker classes available as part of the CocoaPods documentation.

2. Initialization

Assuming you have completed the iOS Tracker Setup for your project, you are now ready to initialze the Snowplow Tracker.

2.1 Importing the library

Adding the library into your project is as simple as adding the headers into your class file:

#import <SnowplowTracker.h>
#import <SnowplowEmitter.h>

If you have manually copied the library into your project, don’t forget to change your import syntax:

#import "SnowplowTracker.h"
#import "SnowplowEmitter.h"

That’s it – you are now ready to initialize a tracker instance.

2.2 Creating a tracker

To instantiate a tracker in your code simply instantiate the SnowplowTracker class with the constructor:

- (id) initWithCollector:(SnowplowEmitter *)collector_
                   appId:(NSString *)appId_
           base64Encoded:(Boolean)encoded
               namespace:(NSString *)namespace_

For example:

SnowplowTracker *t1 = [[SnowplowTracker alloc] initWithCollector:collector appId:@"AF003" base64Encoded:false namespace:@"cloudfront"];
Argument NameDescription
collectorThe SnowplowEmitter object you create
namespaceThe name of the tracker instance
appIdThe application ID
base64EncodedWhether to enable base 64 encoding

2.2.1 collector

This is a single SnowplowEmitter object that will be used to send all the tracking events created by the SnowplowTracker to a collector. See Sending events for more on its configuration.

2.2.2 namespace

If provided, the namespace argument will be attached to every event fired by the new tracker. This allows you to later identify which tracker fired which event if you have multiple trackers running.

2.2.3 appId

The appId argument lets you set the application ID to any string.

2.2.4 base64Encoded

By default, unstructured events and custom contexts are encoded into Base64 to ensure that no data is lost or corrupted. You can turn encoding on or off using the Boolean base64Encoded argument.

3. Adding extra data

Unlike the other Trackers, the iOS tracker automatically collects your platform, screen resolution, viewport, color depth, timezone and language from the device. You can still however, set your user ID to properly track different users if you require it.

3.1 Set user ID with setUserId

You can set the user ID to any string:

s1.setUserId( "{{USER ID}}" )

Example:

[tracker setUserId:@"alexd"];

3.2 Sending IFA

Apps that do not display advertisements are not allowed to access Apple’s Identifier For Advertisers (IFA). For this reason, the Snowplow iOS Tracker will only send IFA as part of the mobile_context which is attached to each event if you have the AdSupport.framework included in your app (and are therefore intending to serve ads).

For the avoidance of doubt, you can also avoid sending IFA regardless of your advertising situation, thus:

  • Click on Build Settings to your app’s project in Xcode
  • Search for Preprocessor Macros
  • Add a macro defined asSNOWPLOW_NO_IFA = 1

4. Tracking specific events

Snowplow has been built to enable you to track a wide range of events that occur when users interact with your websites and apps. We are constantly growing the range of functions available in order to capture that data more richly.

Tracking methods supported by the iOS Tracker at a glance:

Function*Description
trackScreenView:Track the user viewing a screen within the application
trackPageView:Track and record views of web pages.
trackEcommerceTransaction:Track an ecommerce transaction and its items
trackStructuredEvent:Track a Snowplow custom structured event
trackUnstructuredEvent:Track a Snowplow custom unstructured event
trackTiming:Track a Snowplow user timing event

4.1 Common

All events are tracked with specific methods on the tracker instance, of the form trackXXX(), where XXX is the name of the event to track.

4.1.1 Custom contexts

In short, custom contexts let you add additional information about the circumstances surrounding an event in the form of an NSDictionary object. Each tracking method accepts an additional optional contexts parameter after all the parameters specific to that method:

- (void) trackPageView:(NSString *)pageUrl
                 title:(NSString *)pageTitle
              referrer:(NSString *)referrer;
- (void) trackPageView:(NSString *)pageUrl
                 title:(NSString *)pageTitle
              referrer:(NSString *)referrer
               context:(NSMutableArray *)context;
- (void) trackPageView:(NSString *)pageUrl
                 title:(NSString *)pageTitle
              referrer:(NSString *)referrer
             timestamp:(double)timestamp;
- (void) trackPageView:(NSString *)pageUrl
                 title:(NSString *)pageTitle
              referrer:(NSString *)referrer
               context:(NSMutableArray *)context
             timestamp:(double)timestamp;

The context argument should consist of a NSArray of NSDictionary representing an array of one or more contexts. The format of each individual context element is the same as for an unstructured event.

If a visitor arrives on a page advertising a movie, the context dictionary might look like this:

{
  "schema": "iglu:com.acme_company/movie_poster/jsonschema/2.1.1",
  "data": {
    "movieName": "The Guns of Navarone",
    "posterCountry": "US",
    "posterYear": "1961"
  }
}

The corresponding NSDictionary would look like this:

NSDictionary *poster = @{
                         @"schema":@"iglu:com.acme_company/movie_poster/jsonschema/1-0-0",
                         @"data": @{
                                 @"movieName": @"The Guns of Navarone",
                                 @"posterCountry": @"US",
                                 @"posterYear": @"1961"
                                 }
                         };

Sending the movie poster context with an event looks like this:

[tracker trackStructuredEvent:@"Product"
                       action:@"View"
                        label:nil
                     property:nil
                        value:0
                      context:[NSMutableArray arrayWithArray:@[poster]]];

Note that even if there is only one custom context attached to the event, it still needs to be placed in an array.

4.1.2 Optional timestamp & context argument

In all the trackers, we offer a way to set the timestamp if you want the event to show as tracked at a specific time. If you don’t, we create a timestamp while the event is being tracked.

Here is an example:

[tracker trackPageView:@"www.page.com" title:@"Example Page" referrer:@"www.referrer.com"];

[tracker trackPageView:@”www.page.com title:@”Example Page referrer:@”www.referrer.com context:contextArray]

;

[tracker trackPageView:@”www.page.com title:@”Example Page referrer:@”www.referrer.com timestamp:1234567890]

;

[tracker trackPageView:@”www.page.com title:@”Example Page referrer:@”www.referrer.com context:contextArray timestamp:1234567890]

;

4.1.3 Tracker method return values

To be confirmed. As of now, trackers do not return anything.

4.2 Track screen views with trackScreenView:

Use trackScreenView: to track a user viewing a screen (or equivalent) within your app. Arguments are:

ArgumentDescriptionRequired?Validation
nameHuman-readable name for this screenNoNSString*
id_Unique identifier for this screenNoNSString*
contextCustom context for the eventNoNSMutableArray*
timestampOptional timestamp for the eventNodouble

Example:

[t1 trackScreenView:@"HUD > Save Game" screen:@"screen23"];

[t1 trackScreenView:@”HUD > Save Game screen:nil timestamp:12435678]

;

[t1 trackScreenView:@”HUD > Save Game screen:@”screen23 timestamp:12435678]

;

4.3 Track pageviews with trackPageView:

Use trackPageView: to track a user viewing a page within your app.

Arguments are:

ArgumentDescriptionRequired?Validation
pageUrlThe URL of the pageYesNSString*
pageTitleThe title of the pageYesNSString*
referrerThe address which linked to the pageYesNSString*
contextCustom context for the eventNoNSMutableArray*
timestampOptional timestamp for the eventNodouble

Example:

[t1 trackPageView:@"www.example.com" title:@"example" referrer:@"www.referrer.com" context:contextList];

[t1 trackPageView:@”www.example.com title:@”example referrer:@”www.referrer.com]

;

4.4 Track ecommerce transactions with trackEcommerceTransaction:

Use trackEcommerceTransaction: to track an ecommerce transaction. Arguments:

ArgumentDescriptionRequired?Validation
orderIdID of the eCommerce transactionYesNSString*
totalValueTotal transaction valueYesfloat
affiliationTransaction affiliationNoNSString*
taxValueTransaction tax valueNofloat
shippingDelivery cost chargedNofloat
cityDelivery address cityNoNSString*
stateDelivery address stateNoNSString*
countryDelivery address countryNoNSString*
currencyTransaction currencyNoNSString*
itemsItems in the transactionYesNSMutableArray*
contextCustom context for the eventNoNSMutableArray*
tstampWhen the transaction event occurredNodouble

trackEcommerceTransaction: fires multiple events: one “transaction” event for the transaction as a whole, and one “transaction item” event for each element of the items array. Each transaction item event will have the same timestamp, orderId, and currency as the main transaction event.

The items argument is an NSMutableArray containing an NSDictionary for each item in the transaction. There is a convenience constructor for each item called trackEcommerceTransactionItem:. Arguments:

FieldDescriptionRequired?Validation
skuItem SKUYesNSString*
priceItem priceYesfloat
quantityItem quantityYesfloat
nameItem nameNoNSString*
categoryItem categoryNoNSString*
contextCustom context for the eventNoNSMutableArray*
currencyTransaction currencyNoNSString*
contextCustom context for the eventNoNSMutableArray*
tstampWhen the transaction event occurredNodouble

Example of tracking a transaction containing one item:

NSString *transactionID = @"6a8078be";
NSMutableArray *itemArray = [NSMutableArray array];

[itemArray addObject:[t trackEcommerceTransactionItem:transactionID
                                                  sku:@"pbz0026"
                                                 name:@"Hot Chocolate"
                                             category:@"Drink"
                                                price:0.75F
                                             quantity:1
                                             currency:@"USD"]];

[t trackEcommerceTransaction:transactionID
totalValue:350
affiliation:@”no_affiliate
taxValue:10
shipping:15
city:@”Boston
state:@”Massachusetts
country:@”USA
currency:@”USD
items:itemArray]

;

4.5 Track structured events with trackStructuredEvent:

Use trackStructuredEvent: to track a custom event happening in your app which fits the Google Analytics-style structure of having up to five fields (with only the first two required):

ArgumentDescriptionRequired?Validation
categoryThe grouping of structured events which this action belongs toYesNSString*
actionDefines the type of user interaction which this event involvesYesNSString*
labelA string to provide additional dimensions to the event dataYesNSString*
propertyA string describing the object or the action performed on itYesNSString*
valueA value to provide numerical data about the eventYesint
contextCustom context for the eventNoNSMutableArray*
timestampOptional timestamp for the eventNodouble

Example:

[t1 trackStructuredEvent:@"shop" action:@"add-to-basket" label:@"Add To Basket" property:@"pcs" value:27];

[t1 trackStructuredEvent:@”shop action:@”add-to-basket label:@”Add To Basket property:@”pcs value:27 timestamp:1234569]

;

4.6 Track unstructured events with trackUnstructuredEvent:

Custom unstructured events are a flexible tool that enable Snowplow users to define their own event types and send them into Snowplow.

When a user sends in a custom unstructured event, they do so as a JSON of name-value properties, that conforms to a JSON schema defined for the event earlier.

Use trackUnstructuredEvent: to track a custom event which consists of a name and an unstructured set of properties. This is useful when:

  • You want to track event types which are proprietary/specific to your business (i.e. not already part of Snowplow), or
  • You want to track events which have unpredictable or frequently changing properties

The arguments are as follows:

ArgumentDescriptionRequired?Validation
eventJsonThe properties of the eventYesNSDictionary*
contextCustom context for the eventNoNSMutableArray*
timestampOptional timestamp for the eventNodouble

Example:

- (void) trackUnstructuredEvent:(NSDictionary *)eventJson
                        context:(NSMutableArray *)context
                      timestamp:(double)timestamp;

If you supply a NSDictionary*, make sure that this top-level contains your schema and data keys, and then store your data properties as a child NSDictionary*.

Example:

NSDictionary *event = @{
                          @"schema":@"iglu:com.acme/save_game/jsonschema/1-0-0",
                          @"data": @{
                                  @"level": @23,
                                  @"score": @56473
                                  }
                          };
tracker trackUnstructuredEvent:event
                        context:nil
                      timestamp:12345678;

For more on JSON schema, see the blog post.

4.7 Track user timings with trackTimingWithCategory:

Use trackTiming: to track a user timing in your app – for example, how long a game took to load, or how long an in-app purchase took to download. The fields are as follows:

ArgumentDescriptionRequired?Validation
categoryCategorizing timing variables into logical groups (e.g API calls, asset loading)YesNSString*
variableIdentify the timing being recordedYesNSString*
timingThe number of milliseconds in elapsed time to reportYesNSUInteger
labelOptional description of this timingYesNSString*
contextCustom context for the eventNoNSMutableArray*
timestampOptional timestamp for the eventNodouble

Example:

[t1 trackTimingWithCategory:@"Application"
                   variable:@"Background"
                     timing:324
                      label:@"5231804123"];

[t1 trackTimingWithCategory:@”Application
variable:@”Background
timing:324
label:@”5231804123
timestamp:1234569]

;

5. Sending events: SnowplowEmitter

Events created by the Tracker are sent to a collector using a SnowplowEmitter instance. You can create one using one of the init methods:

- (id) initWithURLRequest:(NSURL *)url
               httpMethod:(NSString *)method
             bufferOption:(enum SnowplowBufferOptions)option;
- (id) initWithURLRequest:(NSURL *)url
               httpMethod:(NSString* )method;

For example:

NSURL *url = [[NSURL alloc] initWithString:@"https://collector.acme.net"];
SnowplowEmitter emitter = [[SnowplowEmitter alloc] initWithURLRequest:url
                                                           httpMethod:@"POST"
                                                         bufferOption:SnowplowBufferInstant];
SnowplowEmitter emitter2 = [[SnowplowEmitter alloc] initWithURLRequest:url
                                                            httpMethod:@"GET"];

5.1 Using a buffer

A buffer is used to group events together in bulk before sending them. This is especially handy to reduce network usage. By default, the SnowplowEmitter buffers up to 10 events before sending them.

You can set this during the creation of a SnowplowEmitter object or using the setter -(void)setBufferOption:

NSURL *url = [[NSURL alloc] initWithString:@"https://collector.acme.net"];
SnowplowEmitter emitter = [[SnowplowEmitter alloc] initWithURLRequest:url
                                                           httpMethod:@"POST"
                                                         bufferOption:SnowplowBufferInstant];
SnowplowEmitter emitter2 = [[SnowplowEmitter alloc] initWithURLRequest:url
                                                           httpMethod:@"POST"
                                                         bufferOption:SnowplowBufferDefault];

[emitter setBufferOption:SnowplowBufferInstant]

;

Here are all the posibile options that you can use:

OptionDescription
SnowplowBufferInstantEvents are sent as soon as they are created
SnowplowBufferDefaultSends events in a group when 10 events are created

5.2 Choosing the HTTP method

Snowplow supports receiving events via GET requests, but will soon have POST support. In a GET request, each event is sent in individual request. With POST requests, events are bundled together in one request.

Here are all the posibile options that you can use:

OptionDescription
@"GET"Events are sent individually as GET requests
@"POST"Events are sent in a group when 10 events are received in one POST request

5.3 Sending HTTP requests

You can set this during the creation of a SnowplowEmitter object:

NSURL *url = [[NSURL alloc] initWithString:@"https://collector.acme.net"];
SnowplowEmitter emitter = [[SnowplowEmitter alloc] initWithURLRequest:url
                                                           httpMethod:@"POST"
                                                         bufferOption:SnowplowBufferInstant];
SnowplowEmitter emitter2 = [[SnowplowEmitter alloc] initWithURLRequest:url
                                                           httpMethod:@"GET"
                                                         bufferOption:SnowplowBufferDefault];