assemblyscript-json

JSON encoder / decoder for AssemblyScript.

Special thanks to https://github.com/MaxGraey/bignum.wasm for basic unit testing infra for AssemblyScript.

Installation

assemblyscript-json is available as a npm package. You can install assemblyscript-json in your AssemblyScript project by running:

npm install --save assemblyscript-json

Usage

Parsing JSON

import { JSON } from "@devcycle/assemblyscript-json"; 

// Parse an object using the JSON object
let jsonObj: JSON.Obj = <JSON.Obj>(JSON.parse('{"hello": "world", "value": 24}'));

// We can then use the .getX functions to read from the object if you know it's type
// This will return the appropriate JSON.X value if the key exists, or null if the key does not exist
let worldOrNull: JSON.Str | null = jsonObj.getString("hello"); // This will return a JSON.Str or null
if (worldOrNull != null) {
  // use .valueOf() to turn the high level JSON.Str type into a string
  let world: string = worldOrNull.valueOf();
}

let numOrNull: JSON.Num | null = jsonObj.getNum("value");
if (numOrNull != null) {
  // use .valueOf() to turn the high level JSON.Num type into a f64
  let value: f64 = numOrNull.valueOf();
}

// If you don't know the value type, get the parent JSON.Value
let valueOrNull: JSON.Value | null = jsonObj.getValue("hello");
  if (valueOrNull != null) {
  let value = <JSON.Value>valueOrNull;

  // Next we could figure out what type we are
  if(value.isString) { 
    // value.isString would be true, so we can cast to a string
    let innerString = (<JSON.Str>value).valueOf();
    let jsonString = (<JSON.Str>value).stringify();

    // Do something with string value
  }
}

Encoding JSON

import { JSONEncoder } from "@devcycle/assemblyscript-json";

// Create encoder
let encoder = new JSONEncoder();

// Construct necessary object
encoder.pushObject("obj");
encoder.setInteger("int", 10);
encoder.setString("str", "");
encoder.popObject();

// Get serialized data
let json: Uint8Array = encoder.serialize();

// Or get serialized data as string
let jsonString: string = encoder.stringify();

assert(jsonString, '"obj": {"int": 10, "str": ""}'); // True!

Custom JSON Deserializers

import { JSONDecoder, JSONHandler } from "@devcycle/assemblyscript-json";

// Events need to be received by custom object extending JSONHandler.
// NOTE: All methods are optional to implement.
class MyJSONEventsHandler extends JSONHandler {
  setString(name: string, value: string): void {
    // Handle field
  }

  setBoolean(name: string, value: bool): void {
    // Handle field
  }

  setNull(name: string): void {
    // Handle field
  }

  setInteger(name: string, value: i64): void {
    // Handle field
  }

  setFloat(name: string, value: f64): void {
    // Handle field
  }

  pushArray(name: string): bool {
    // Handle array start
    // true means that nested object needs to be traversed, false otherwise
    // Note that returning false means JSONDecoder.startIndex need to be updated by handler
    return true;
  }

  popArray(): void {
    // Handle array end
  }

  pushObject(name: string): bool {
    // Handle object start
    // true means that nested object needs to be traversed, false otherwise
    // Note that returning false means JSONDecoder.startIndex need to be updated by handler
    return true;
  }

  popObject(): void {
    // Handle object end
  }
}

// Create decoder
let decoder = new JSONDecoder<MyJSONEventsHandler>(new MyJSONEventsHandler());

// Create a byte buffer of our JSON. NOTE: Deserializers work on UTF8 string buffers.
let jsonString = '{"hello": "world"}';
let jsonBuffer = Uint8Array.wrap(String.UTF8.encode(jsonString));

// Parse JSON
decoder.deserialize(jsonBuffer); // This will send events to MyJSONEventsHandler

Feel free to look through the tests for more usage examples.

Reference Documentation

Reference API Documentation can be found in the docs directory.

License

MIT