Type Definition arrow_array::builder::StringDictionaryBuilder

pub type StringDictionaryBuilder<K> = GenericByteDictionaryBuilder<K, GenericStringType<i32>>;

Builder for DictionaryArray of StringArray

// Create a dictionary array indexed by bytes whose values are Strings.
// It can thus hold up to 256 distinct string values.


let mut builder = StringDictionaryBuilder::<Int8Type>::new();

// The builder builds the dictionary value by value
builder.append("abc").unwrap();
builder.append_null();
builder.append("def").unwrap();
builder.append("def").unwrap();
builder.append("abc").unwrap();
let array = builder.finish();

assert_eq!(
  array.keys(),
  &Int8Array::from(vec![Some(0), None, Some(1), Some(1), Some(0)])
);

// Values are polymorphic and so require a downcast.
let av = array.values();
let ava: &StringArray = av.as_any().downcast_ref::<StringArray>().unwrap();

assert_eq!(ava.value(0), "abc");
assert_eq!(ava.value(1), "def");