Why Can't I Directly Modify Values in a Go Range Loop Over a Struct Slice?

Why is it Impossible to Modify Values in a Range of Type Structure?

This programming query arises from the inability to alter values within a range of a structured type in the Go programming language. Understanding this issue requires a closer examination of how slices and ranges operate in Go.

Despite your initial method of loading data into the chartRecords array, modifying values in the loop doesn't seem to have any effect. The output, instead of reflecting the modified values, retains the original values.

The confusion stems from the way Go handles slices and ranges. For a range clause in a for statement, Go assigns iteration values to corresponding iteration variables, but those changes are only applied within the block. These iteration variables are copies, not references to the original slice elements.

To make permanent changes to the slice elements, the modified values from the iteration variable must be explicitly assigned back into the slice. Here's the updated code:

for i, elem := range chartRecords {
    elem.Count = modMe(mod, i)
    chartRecords[i] = elem
}

In this modified loop, the values modified in the iteration variable elem are assigned back into the original slice chartRecords, ensuring that the changes are persistent.

The above is the detailed content of Why Can't I Directly Modify Values in a Go Range Loop Over a Struct Slice?. For more information, please follow other related articles on the PHP Chinese website!