dinimar commented on issue #14939:
URL: https://github.com/apache/arrow/issues/14939#issuecomment-1464481799
@rok @pitrou @benibus Hi, I'm a newbie and stuck at implementing
`FieldPath::Get(const Table & table)`
Test case code:
```
...
for (int index = 0; index < tablePtr->num_columns(); ++index) {
ASSERT_OK_AND_ASSIGN(auto fieldPathColumn,
FieldPath({index}).Get(*tablePtr));
EXPECT_TRUE(fieldPathColumn->Equals(tablePtr->column(index)));
}
...
```
Currently, I have the following implementation for this function:
```
Result<std::shared_ptr<ChunkedArray>> FieldPath::Get(const Table& table)
const {
ARROW_ASSIGN_OR_RAISE(auto data, FieldPathGetImpl::Get(this,
table.columns()));
return data;
}
```
And the following `FieldPathGetImpl::Get` implementation:
```
static Result<std::shared_ptr<ChunkedArray>> Get(const FieldPath* path,
const ChunkedArrayVector&
table) {
return FieldPathGetImpl::Get(
path, &table,
[](const std::shared_ptr<ChunkedArray>& data) {
return data;
});
}
```
For the function above I got the following compilation error:
```
\arrow\cpp\src\arrow\type.cc(1136,1): error C2440: '=': cannot convert from
'std::shared_ptr<arrow::ChunkedArray>' to 'const
std::vector<std::shared_ptr<arrow::ChunkedArray>,std::allocator<std::shared_ptr<arrow::ChunkedArray>>>
*'
```
related code:
```
template <typename T, typename GetChildren>
static Result<T> Get(const FieldPath* path, const std::vector<T>* children,
GetChildren&& get_children, int* out_of_range_depth) {
...
out = &children->at(index);
children = get_children(*out); // line 1136
++depth;
}
return *out;
}
```
Implementations with no using `Result<T> FieldPathGetImpl::Get(const
FieldPath* path, const std::vector<T>* children,
GetChildren&& get_children, int* out_of_range_depth)`
will violate DRY principle by creating non-template functions specifically for
Table or putting implementation of template function right in `Get(const
FieldPath* path,
const ChunkedArrayVector&
table) `
Any help would be appreciated. Other functions are implemented and tested by
unit tests
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