Why Can't I Modify Struct Values Directly Within a Go Range Loop?

Understanding Range Variables in Go

Q: Why am I unable to modify values within a range of type structure?

In Go, the concept of slices and ranges can be confusing for newcomers. A range statement iterates through elements in a collection, assigning them to iteration variables. However, in the case of a structure, modifying these variables does not modify the original values.

A: Assigning Iteration Variables

The Go Programming Language Specification states that for statements with a range clause, iteration variables are assigned the values of each element in the collection. However, these variables are only local to the loop body.

Modifying Iteration Variables

When you modify an iteration variable within a loop, you are not actually modifying the original value in the collection. Instead, you are creating a new copy of the value and assigning it to the iteration variable.

Solution: Assigning Modified Values

To modify the original values in the collection, you need to assign the modified iteration variables back to the original collection. In the example code, the modified iteration variable for elem.Count needs to be assigned back to chartRecords[i].

Updated Code

Here is the updated code with the necessary modification:

This modification ensures that the modified elem.Count value is properly assigned back to the chartRecords slice.

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