Channel Directions

By default, channels are bidirectional (you can send and receive). However, you can use directional channel types to restrict how a channel is used within a specific function.

Read-Only Channels

A read-only channel is denoted by the arrow pointing away from the chan keyword.

func processData(ch <-chan int) {
    // This function can ONLY receive from ch
    // ch <- 42 // This would cause a compile error
}

Write-Only Channels

A write-only channel is denoted by the arrow pointing toward the chan keyword.

func fetchData(ch chan<- int) {
    // This function can ONLY send to ch
    // <-ch // This would cause a compile error
}

Why use directions?

• Type Safety: The compiler ensures that a receiver doesn’t accidentally send data, or a sender doesn’t accidentally receive.
• Clear Intent: Directional types act as documentation for your functions’ behavior.
• API Contracts: You can pass a bidirectional channel to a function that only accepts a directional one; Go will handle the conversion automatically.