Which features are available in this library?
This is an optional library you can install if you're working with Ruby. It uses an internal queue to make calls fast and non-blocking. It also batches requests and flushes asynchronously, making it perfect to use in any part of your web app or other server-side application that needs performance.
Installation
Add this to your Gemfile
:
gem "posthog-ruby"
In your app, set your API key before making any calls. If setting a custom api_host
, make sure to include the protocol (e.g. https://
).
posthog = PostHog::Client.new({api_key: "<ph_project_api_key>",api_host: "<ph_instance_address>", # You can remove this line if you're using app.posthog.comon_error: Proc.new { |status, msg| print msg }})
You can find your key in the 'Project Settings' page in PostHog.
Making calls
Capture
Capture allows you to capture anything a user does within your system, which you can later use in PostHog to find patterns in usage, work out which features to improve or where people are giving up.
A capture
call requires:
distinct id
which uniquely identifies your userevent name
to specify the event
- We recommend naming events with "[noun][verb]", such as
movie played
ormovie updated
, in order to easily identify what your events mean later on (we know this from experience).
Optionally you can submit:
properties
, which is a dictionary with any information you'd like to addtimestamp
, a datetime object for when the event happened. If this isn't submitted, it'll be set to the current time
For example:
posthog.capture({distinct_id: 'distinct id',event: 'movie played',properties: {movie_id: '123',category: 'romcom'}})
Setting user properties via an event
To set properties on your users via an event, you can leverage the event properties $set
and $set_once
.
$set
Example
posthog.capture({distinct_id: 'distinct id',event: 'movie played',properties: {$set: { userProperty: 'value' }}})
Usage
When capturing an event, you can pass a property called $set
as an event property, and specify its value to be an object with properties to be set on the user that will be associated with the user who triggered the event.
$set_once
Example
posthog.capture({distinct_id: 'distinct id',event: 'movie played',properties: {$set_once: { userProperty: 'value' }}})
Usage
$set_once
works just like $set
, except that it will only set the property if the user doesn't already have that property set.
Identify
We highly recommend reading our section on Identifying users to better understand how to correctly use this method.
Identify lets you add metadata to your users so you can easily identify who they are in PostHog, as well as do things like segment users by these properties.
An identify
call requires:
distinct id
which uniquely identifies your userproperties
with a dict with any key:value pairs
For example:
posthog.identify({distinct_id: "user:123",properties: {email: 'john@doe.com',pro_user: false}})
The most obvious place to make this call is whenever a user signs up, or when they update their information.
Alias
To connect whatever a user does before they sign up or log in with what they do after you need to make an alias call. This will allow you to answer questions like "Which marketing channels leads to users churning after a month?" or "What do users do on our website before signing up?"
In a purely back-end implementation, this means whenever an anonymous user does something, you'll want to send a session ID with the capture call. Then, when that users signs up, you want to do an alias call with the session ID and the newly created user ID.
The same concept applies for when a user logs in.
If you're using PostHog in the front-end and back-end, doing the identify
call in the frontend will be enough.
An alias
call requires:
previous distinct id
: the unique ID of the user from beforehanddistinct id
: the current unique id
For example:
posthog.alias({distinct_id: "user:123",alias: "user:12345",})
Sending page views
If you're aiming for a full back-end implementation of PostHog, you can send pageviews from your backend
posthog.capture({distinct_id: 'distinct id',event: '$pageview',properties: {'$current_url': 'https://example.com'}})
Feature flags
Note that to use feature flags you must specify
personal_api_key
when initializing PostHog.
Checking if a feature is enabled
To check if a feature flag is on for a given user, you can call is_feature_enabled
, passing the flag's key and the user's distinct ID. You can optionally pass a third argument to override the default result to be returned if the flag is not found. This is set to false
by default.
# If a flag is not found, the default return value is `false`.# You can override this by passing `true` as the third argument to is_feature_enabledis_my_flag_enabled = posthog.is_feature_enabled('flag-key', 'user distinct id')if is_my_flag_enabled# Do something differently for this userend
If your feature flag relies entirely on rollout percentage (i.e. it has no filters),
is_feature_enabled
will provide a fast response, allowing it to be used in the logic for API endpoints, for example. Flags that depend on filters require a call to the PostHog API so will take longer.
Reloading feature flags
When initializing PostHog, you can configure the interval at which feature flags are polled (fetched from the server). However, if you need to force a reload, you can use reloadFeatureFlags
:
posthog.reload_feature_flags()// Do something with feature flags here
Thank you
This library is largely based on the analytics-ruby
package.