How to decode json into a Codable to use in a SwiftUI Preview?

Question

Wondering if there is a way to decode some json into a Codable that is a dependency of a View so i can use swiftUI previews?

Here is a working unit test for the codable

    func testDecode() {
        let data = Data(jsonProj.utf8)
        //frmt
        let frmt2 = DateFormatter()
        frmt2.dateFormat = "yyyy-MM-dd'T'HH:mm:ss.SSSX"
        //decoder
        let decoder = JSONDecoder()
        decoder.dateDecodingStrategy = .custom({ (decoder) -> Date in
            let container = try decoder.singleValueContainer()
            let dateStr = try container.decode(String.self)
            guard let d = frmt2.date(from: dateStr) else { fatalError() } //fixme some danger here
            return d
        })
        do {
            let p = try decoder.decode(Project.self, from: data)
            XCTAssertEqual(p.id, 2)
            print(p)
        }
        catch {
            print(error)
            XCTFail()
        }
    }

I'd like to use it here

struct PreProjectCell_Previews: PreviewProvider {

   //static let decodedJson: Project ... NEED THIS PART

    static var previews: some View {
        NavigationView {
            List {
                PreProjectCell(project: <#Project#>)
            }
        }
    }
}

jjatie · Accepted Answer · 2021-06-10 17:37:25Z

2

extension Project {
    static var preview: Self {
        let data = Data(jsonProj.utf8)
        //frmt
        let frmt2 = DateFormatter()
        frmt2.dateFormat = "yyyy-MM-dd'T'HH:mm:ss.SSSX"
        //decoder
        let decoder = JSONDecoder()
        decoder.dateDecodingStrategy = .custom({ (decoder) -> Date in
            let container = try decoder.singleValueContainer()
            let dateStr = try container.decode(String.self)
            guard let d = frmt2.date(from: dateStr) else { fatalError() } //fixme some danger here
            return d
        })
        return try! decoder.decode(Self.self, from: data)
    }
}

Then in your SwiftUI Preview you can do:

struct PreProjectCell_Previews: PreviewProvider {
    static var previews: some View {
        NavigationView {
            List {
                PreProjectCell(project: .preview)
            }
        }
    }
}

answered Jun 10, 2021 at 17:37

jjatie

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1 Comment

aaronium112 Over a year ago

nice 1. very swift!

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