Kotlin中函数调用赋值给变量时是否会立即执行该函数？

Great question! Let’s break this down with your exact example to make it crystal clear.

First, let’s clarify the core behavior:
When you write val userData = GraphRequest.newMeRequest(...), the newMeRequest() function is called immediately at the moment that line of code runs. But here’s the key detail: it doesn’t actually send the Graph API request yet.

What’s happening under the hood: #

newMeRequest is a factory method—its job is to create and return a configured GraphRequest object. This object holds all the details you’ve provided:

• The accessToken for authentication
• Your GraphJSONObjectCallback that defines what to do when the request completes

So userData isn’t storing the result of the request, and it isn’t storing the function itself—it’s storing the pre-configured request object that’s ready to be executed.

When does the actual request run? #

The callback onCompleted won’t fire until you explicitly trigger the request using the GraphRequest object. In most cases, you’ll call:

userData.executeAsync()

This is when the network request is actually sent, and once it finishes, your onCompleted method will log the result as you’ve defined.

A quick side note to avoid confusion: #

If you were dealing with a function that returns a function type (like () -> Unit), assigning it to a variable would store the function itself without executing it. But that’s not the case here—newMeRequest returns a concrete GraphRequest instance, so invoking it creates that instance right away.

To sum up:

• GraphRequest.newMeRequest() runs immediately when you assign it to userData
• It creates a request object (no network call yet)
• You need to call executeAsync() (or similar) on userData to actually send the request and trigger your callback

内容的提问来源于stack exchange，提问作者Zorgan