JSON Overview

JSON Overview

{
  "weather": "sunny",
  "temp": 78,
  "humidity": 32,
  
  "forecast": {
    "mon": {
      "high": 89,
      "low": 54
    }
  },
    
  "daily_temp": [
    89,
    84,
    83
  ]
}

Review

  • We want our device to interact with services all over the internet–e.g. permanently store all heart rate data in the cloud, retrieve the weather forecast tomorrow, etc.
  • APIs provide the mechanism we use to communicate with these other services
  • Webhooks are created in the Particle cloud to connect our Argon to an API online

Review: Process to Interacting with Data from API

width:1000px

Where does JSON come in?

  • Sending one temperature value to a webservice is not hard
  • Sending dozens of sensor every second requires creating much more complex way of representing / store those values so we can send them to the cloud
  • JSON is an excellent, common way we exchange complex data

JSON (JavaScript Object Notation)

  • Popular format for exchanging data with web services
    • XML is another
  • JSON is useful because we can represent complex data with a simple string, and then share that data between two different services
  • JSON is not a programming language; it is a way of representing complex data as a string
  • Typically, programmers use library to read (parse) and write JSON

JSON Overview

  • JSON is a way of representing an object as a text string
  • Built around key-value pair idea (like a dictionary or hash)
  • Two data types
    • objects (single item denoted with { })
    • arrays (multiple items denoted with [ ])

JSON Basics - Objects

{ 
  "weather": "sunny", 
  "temp": 78.000, 
  "humidity": 32 
}
  • JSON objects are formatted { key : value }
  • Keys are always strings
  • Values can be string, int, float, objects, or arrays
    • Ex:"weather" is a key and "sunny" is its value
    • Ex: "sunny" is a string, 78.000 is a float, 32 is an int

JSON Basics - Nested Objects

{ "forecast": {
    "mon": {
      "high": 89,
      "low":54
    }
  }
}
  • Values can be JSON objects
    • Ex: forecast is a key and the value is "mon"
    • "mon" is itself a key which store the keys "high" and low

JSON Basics - Arrays

{ "daily_temp": [
    89,
    84,
    83
  ] 
}
  • Arrays are specified with [ ]
  • Indices begin at 0 and up to length - 1
  • Elements of arrays can be string, int, float, objects, or arrays
    • Ex:"daily_temp" is a key and its value is an array
    • Ex: 89 is an int and is at index0

Credit

Updated: