When to Pass Parameters vs. Use Closures in Go Functions?

Passing Parameters to Function Closure

Function closures in Go allow inner functions to access the variables of the enclosing function. This raises the question: when is it preferable to pass parameters to inner functions instead of using closures?

In the first example, an anonymous function is created with a parameter, a channel. This function sleeps for a short duration before sending a value to the channel. In the second example, an inner function is created as a closure, accessing the channel variable from the outer function.

The choice between these two approaches depends on the intended use case. A parameter is preferred when each function call should receive a distinct value. This is useful when the function is returned as part of a larger function, as the parameter can be customized before the closure is created.

Conversely, a closure is better suited when all function calls should share the same variable. In the provided example, both approaches ultimately achieve the same result of sending a value to the channel after a delay. However, the closure ensures that each goroutine accesses the same shared channel object.

Consider the following example to illustrate the difference:

for i := 0; i < 3; i++ {
    // Closure example: all calls share the same 'i'
    go func() {
        fmt.Println(i)
    }()

    // Parameter example: each call receives a copy of 'i'
    go func(v int) {
        fmt.Println(v)
    }(i)
}

In the closure example, all function calls print '3' as the value of 'i' may have changed by the time the goroutines execute. In the parameter example, each call receives a copy of 'i' from when the function was created, resulting in values '0', '1', and '2'.

Ultimately, the decision between using a closure or a parameter depends on the specific use case and the desired sharing of variables between the enclosing and inner functions.

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