Assignment Expressions

Flow-Wing provides the following assignment operators:

• = Used for Updating Variables
• <- Used for Complete Reassignment of Variables

Assignment expressions in Flow-Wing allow updating the value of a variable. The assignment operator (=) is used to set a variable to a new value.

var x = 10
x = 20

= Behavior for Complex Types (Container / Objects)

Example:

type Person = {
  name: str,
  age: int,
}

var person: Person =  { name: "Alice", age: 30 }

person = { name: "Bob" }

print(person)

Output:

{ name : 'Bob', age : 30 }

The value of person is updated to {"name": "Bob", "age": 30}. In this case, only the value of name is updated, while the rest of the properties remain the same. If we want to change the entire person object, we can use person = {"name": "Bob", "age": 30} or we can use the <- operator.

The <- operator is used to update the variable completely. For primitive types, the behavior of <- is similar to that of =, but for complex types, the behavior of <- is different.

Example:

type Person = {
  name: str,
  age: int,
}

var person: Person =  { name: "Alice", age: 30 }

person <- { name: "Bob" }

print(person)

The value of person is updated to {"name": "Bob", "age": 0}. The age property is set to 0 since it was not provided, so it defaults to this value.

Container Example:

Using <- for Assignment

type Person = {
  name: str,
  age: int,
}

var person: Person =  { name: "Alice", age: 30 }

var people: Person[2] = [person, { name: "Bob", age: 30 }]

people <- [{ name: "Charlie", age: 30 }]

print(people) 

Output:

[{ name : 'Charlie', age : 30 }, { name : '', age : 0 }]

The value of the first element in people is updated to {"name": "Charlie", "age": 30}, while the rest are set to their default values.

Using = for Assignment

var people: Person[2] = [person, { name: "Bob", age: 30 }]

people = [{ name: "Charlie", age: 30 }]

print(people) 

Output:

[{ name : 'Charlie', age : 30 }, { name : 'Bob', age : 30 }]