> For the complete documentation index, see [llms.txt](https://docs.hackle.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.hackle.io/en/development-guide/ios/event-tracking.md).

# Event Tracking

The Hackle SDK provides the ability to send user events to Hackle. By using this feature at every point where user behavior changes, you can obtain meaningful data about user actions, and use that data to analyze user behavior.

## track

Pass the **Event Key** to the `track()` method to send a user event.

<table><thead><tr><th width="150">Parameter</th><th width="120">Type</th><th>Description</th></tr></thead><tbody><tr><td>Event name (key)</td><td><code>string</code></td><td>Required. Maximum 128 characters.</td></tr></tbody></table>

#### Example

Assume you have defined an event key called `purchase` to collect events when a user clicks the purchase button.

{% tabs %}
{% tab title="Swift" %}

```swift
hackleApp.track(eventKey: "purchase")
```

{% endtab %}

{% tab title="Objective-C" %}

```objectivec
[hackleApp trackWithEventKey:@"purchase"];
```

{% endtab %}
{% endtabs %}

### Property

The Hackle SDK supports adding properties to Event objects.

* Properties must be sent as key-value pairs (Property Key and Property Value).
* A maximum of 64 properties can be added to an event object.

<table><thead><tr><th width="133.04296875">Category</th><th width="127.60546875">Type</th><th>Constraints</th></tr></thead><tbody><tr><td>Property Key</td><td><code>string</code></td><td><ul><li>Character limit is 128 characters.</li><li>Case-insensitive.</li><li>For example, AGE and age are recognized as the same Property Key.</li></ul></td></tr><tr><td>Property Value</td><td><code>boolean</code>, <code>string</code>, <code>number</code>, <code>array</code></td><td><ul><li>For string type, the character limit is 1024 characters.</li><li>String type is case-sensitive.</li><li>For example, APPLE and apple are recognized as different Property Values.</li><li>For number type, up to 15 integer digits and up to 6 decimal places are supported.</li></ul></td></tr></tbody></table>

#### Example

The example below shows three properties being added: `pay_method`, `discount_amount`, and `is_discount`.

{% tabs %}
{% tab title="Swift" %}

```swift
let event = Hackle.event(
                    key: "purchase",
                    properties: [
                        "pay_method": "CARD",
                        "discount_amount": 800,
                        "is_discount": true
                    ])

// 빌더 패턴
let event2 = Event.builder("purchase")
    .property("pay_method": "credit")
    .build()

hackleApp.track(event: event)
hackleApp.track(event: event2)
```

{% endtab %}

{% tab title="Objective-C" %}

```objectivec
HackleEvent *event = [Hackle eventWithKey:@"purchase"
                       value:3200.0
                       properties:@{
                           @"pay_method": @"CARD",
                           @"discount_amount": @800,
                           @"is_discount": @true
                       }];

[hackleApp trackWithEvent:event];
```

{% endtab %}
{% endtabs %}


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