ES6 - Use getters and setters to Control Access to an Object

JavaScript
1

Can someone help me to understand the setter line here. Why do we convert to fahrenheit if we already passed this value through the constructor.

Your code so far

// Only change code below this line
class Thermostat {
  constructor (fahrenheit) {
    this._fahrenheit= fahrenheit;
  }
  //get
  get temperature() {
    return 5/9 * (this._fahrenheit - 32);
  }
  //set
  set temperature (celcius) {
    this._fahrenheit = celcius * 9.0 / 5 + 32
  }
}
// Only change code above this line

const thermos = new Thermostat(76); // Setting in Fahrenheit scale
let temp = thermos.temperature; // 24.44 in Celsius
thermos.temperature = 26;
temp = thermos.temperature; // 26 in Celsius

console.log(temp)

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Challenge: ES6 - Use getters and setters to Control Access to an Object

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2

These are used at different times. Initially, when Thermostat object is created it takes the temperature in Fahrenheit. For changing temperature after that, setter will be used:

const thermos = new Thermostat(76);  // initial temperature
thermos.temperature = 26;  // changing temperature uses setter and Celsius
4

by changing temperature do you mean converting? I dont understand the purpose of converting to Fahrenheit if we already have the value

5

Not converting. Ie. some time passes, temperature is no longer as it was, and object needs to reflect that.

6

sorry Iā€™m just not understanding the flow of this code. If time passes what temp is changed first? Does the user input a different temp in celcius and the function internally converts to fahrenheit to update the object.

7

Exactly this. The only way to change the internal temperature is to use the setter, which will make sure the saved temperature will be in correct units.

2 Likes
9

thanks so much for taking the time to explain to me. I understand now!

10

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