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How to format JSON using Codable and pretty printing

Paul Hudson       @twostraws

When you use JSONEncoder and Codable to create JSON from your Swift data, it comes out in a compressed format by default – it has all its excess whitespace removed. This makes it efficient for transferring over the network, but hard to debug because it’s just a big jumble of words.

For debugging purposes, it’s a good idea to enable pretty printing for your encoded JSON, which will tell JSONEncoder to separate everything using line breaks and spaces so you can read it more easily.

To make this happen, set the outputFormatting property of your JSON encoder to be .prettyPrinted, like this:

let encoder = JSONEncoder()
encoder.outputFormatting = .prettyPrinted

Available from iOS 8.0

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