JSON Utilities

QED provides a set of expressive, Moshi-powered utilities for parsing, formatting, and verifying JSON structures. The approach is lean, type-safe, and DSL-friendly.

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Core Functions

QEDJson.fromJson<T>(json: String): T? Parses a JSON string into a Kotlin object of type T.

QEDJson.toJson<T>(value: T): String Serializes a Kotlin object of type T to a JSON string.

QEDJson.prettyJson(value: Any): String Serializes any Kotlin object into indented, human-readable JSON.

QEDJson.compactJson(value: Any): String Serializes any Kotlin object into compact, minified JSON.

QEDJson.writeToFile(file: File, value: Any): String Writes any Kotlin object to a file as JSON.

QEDJson.mapFromJson(json: String): Map<String, Any>? Converts a JSON string to a Map<String, Any>?.

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Extension Functions

fun String.toPrettyJson(): String
fun String.toPrettyJsonOrNull(): String?

fun String.toCompactJson(): String
fun String.toCompactJsonOrNull(): String?

fun LinkedHashMap<String, Any>.toPrettyJson(): String
fun LinkedHashMap<String, Any>.toPrettyJsonOrNull(): String?

fun LinkedHashMap<String, Any>.toCompactJson(): String
fun LinkedHashMap<String, Any>.toCompactJsonOrNull(): String?

fun Any?.toPrettyJson(): String
fun Any?.toPrettyJsonOrNull(): String?

fun Any?.toCompactJson(): String
fun Any?.toCompactJsonOrNull(): String?

fun Map<String, Any>.toPrettyJson(): String
fun Map<String, Any>.toPrettyJsonOrNull(): String?

fun Map<String, Any>.toCompactJson(): String
fun Map<String, Any>.toCompactJsonOrNull(): String?

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Type-Safe Traversal

The get function is overloaded to support clean traversal of nested JSON structures:

fun Any?.get(key: Any): Any?

The parameter type determines which overload is used — passing a String key treats the structure as a JSON object, passing an Int index treats it as a JSON array. This means verbose type casts can be eliminated entirely:

// Without type-safe traversal
expect(result.get("nutrients").asJsonArray().get(0).get("periodvalues").asJsonObject().get(0).asJsonObject().get("nutvalue")).to.equal(40.0)

// With type-safe traversal
expect(result.get("nutrients").get(0).get("periodvalues").get(0).get("nutvalue")).to.equal(40.0)

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Type Helpers

fun Any?.asJsonArray(): List<Any?>
fun Any?.asJsonObject(): Map<String, Any?>
fun Any?.asJsonPrimitive(): Any?

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Usage Example

Given the following JSON response:

{"nutrientlist": [{"nutcode": "ME"}, {"nutcode": "NE"}, {"nutcode": "CP"}]}

Access a nested value:

expect(result.get("nutrientlist").get(0).get("nutcode")).to.equal("ME")

Pretty-print the full result for logging or debugging:

result.toPrettyJsonOrNull()

Produces:

{
    "nutrientlist": [
        {
            "nutcode": "ME"
        },
        {
            "nutcode": "NE"
        },
        {
            "nutcode": "CP"
        }
    ]
}