Combine's 'prepend' operator

Today, I came across a remarkable feature in Combine: the 'prepend' operator. This operator is a tool that enables you to insert values or sequences of values at the start of the output stream of a Combine publisher. It truly is a hidden gem,.

Here is a detailed explanation of the 'prepend' operator in action:

1. Insert Values at the Start:

• With 'prepend,' you can insert one or more values at the very beginning of the publisher's output. These values are emitted before any other elements from the original publisher.

let originalPublisher = Just(3)
let prependedPublisher = Just(1)
    
originalPublisher
    .prepend(prependedPublisher)
    .sink { value in
        print(value) // Output: 1, 3
    }        

2. Combine and Merge Multiple Sources:

• One of the most exciting features of 'prepend' is its ability to work with other publishers. This means you can prepend values from different sources into your data stream.

let originalPublisher = Just(3)
let prependPublisher = Just(1)
let anotherPrependPublisher = Just(2)
    
originalPublisher
    .prepend(prependPublisher, anotherPrependPublisher)
    .sink { value in
        print(value) // Output: 1, 2, 3
    }        

3. Practical Use Cases:

prepend's extremely important in scenarios where you need to inject values, default config, or placeholder data into your Combine pipelines.

and also can be used when dealing with UI i.e: loading initial data before fetching additional data ????? #iOS #Combine #SwiftUI #TIL