react

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React

Implement a basic reactive system.

Reactive programming is a programming paradigm that focuses on how values are computed in terms of each other to allow a change to one value to automatically propagate to other values, like in a spreadsheet.

Implement a basic reactive system with cells with settable values ("input" cells) and cells with values computed in terms of other cells ("compute" cells). Implement updates so that when an input value is changed, values propagate to reach a new stable system state.

In addition, compute cells should allow for registering change notification callbacks. Call a cell’s callbacks when the cell’s value in a new stable state has changed from the previous stable state.

Running the tests

To run the tests run the command go test from within the exercise directory.

If the test suite contains benchmarks, you can run these with the -bench flag:

go test -bench .

Keep in mind that each reviewer will run benchmarks on a different machine, with different specs, so the results from these benchmark tests may vary.

Further information

For more detailed information about the Go track, including how to get help if you're having trouble, please visit the exercism.io Go language page.

Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.

Documentation

Index

• type Canceler
• type Cell
• type ComputeCell
• type InputCell
• type Reactor
  • func New() Reactor

Types

type Canceler

type Canceler interface {
	// Cancel removes the callback.
	Cancel()
}

A Canceler is used to remove previously added callbacks, see ComputeCell.

type Cell

type Cell interface {
	// Value returns the current value of the cell.
	Value() int
}

A Cell is conceptually a holder of a value.

type ComputeCell

type ComputeCell interface {
	Cell

	// AddCallback adds a callback which will be called when the value changes.
	// It returns a Canceler which can be used to remove the callback.
	AddCallback(func(int)) Canceler
}

A ComputeCell always computes its value based on other cells and can call callbacks upon changes.

type InputCell

type InputCell interface {
	Cell

	// SetValue sets the value of the cell.
	SetValue(int)
}

An InputCell has a changeable value, changing the value triggers updates to other cells.

type Reactor

type Reactor interface {
	// CreateInput creates an input cell linked into the reactor
	// with the given initial value.
	CreateInput(int) InputCell

	// CreateCompute1 creates a compute cell which computes its value
	// based on one other cell. The compute function will only be called
	// if the value of the passed cell changes.
	CreateCompute1(Cell, func(int) int) ComputeCell

	// CreateCompute2 is like CreateCompute1, but depending on two cells.
	// The compute function will only be called if the value of any of the
	// passed cells changes.
	CreateCompute2(Cell, Cell, func(int, int) int) ComputeCell
}

A Reactor manages linked cells.

func New

func New() Reactor