在每次循环迭代中重新声明切片是否是错误的做法？

Question

As an example:

for {
    myData := <-myChan
    buf := new(bytes.Buffer)
    encoder := gob.NewEncoder(buf)
    err := encoder.Encode(myData)
    ...

I could put buf := new(... above the for loop to save processor and maybe some memory, but will that cause any problems? Examples I see have the new in the loop.

Edit: for the case above, the encoder could go above the for loop to, so why doesn't it (in examples I've seen)?

Answer 1

The idiomatic Go style would be to write the clearest code possible as long as it solves the problem at hand within its time and space constraints.

In other words, I wouldn't worry about the efficiency here because:

1. The compiler can do clever optimizations that would remove any differences
2. Almost certainly if there are differences, they are negligible

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If you find out that the allocation takes a considerable portion of each loop iteration, then @peterSO's answer below is a good pattern on how to reuse a bytes.Buffer by calling its Reset method.