# Add or update struct field > Supported in: Batch, Faster, Streaming Updates a field of a struct or adds a new field. **Expression categories:** Struct ## Declared arguments * **Expression:** Expression to update struct field with.
*Expression\* * **Locator:** Locate inner elements with multiple entries like \['author', 'email'].
*StructLocator* * **Struct:** The struct to update.
*Expression\* **Output type:** *Struct* ## Examples ### Example 1: Base case **Argument values:** * **Expression:** `value` * **Locator:** flight * **Struct:** `struct` | struct | value | **Output** | | ----- | ----- | ----- | | {
**airline**: {
**id**: NA,
},
} | foo | {
**airline**: {
**id**: NA,
},
**flight**: foo,
} | *** ### Example 2: Base case **Argument values:** * **Expression:** `value` * **Locator:** flight * **Struct:** `struct` | struct | value | **Output** | | ----- | ----- | ----- | | {
**airline**: {
**id**: FE,
},
} | {
**id**: 1,
} | {
**airline**: {
**id**: FE,
},
**flight**: {
**id**: 1,
},
} | *** ### Example 3: Base case **Argument values:** * **Expression:** `value` * **Locator:** airline.id * **Struct:** `struct` | struct | value | **Output** | | ----- | ----- | ----- | | {
**airline**: {
**id**: NA,
},
} | 1 | {
**airline**: {
**id**: 1,
},
} | | {
**airline**: {
**id**: FE,
},
} | 2 | {
**airline**: {
**id**: 2,
},
} | *** ### Example 4: Null case **Argument values:** * **Expression:** `value` * **Locator:** airline.id * **Struct:** `struct` | struct | value | **Output** | | ----- | ----- | ----- | | *null* | *null* | *null* | | *null* | 1 | *null* | | {
**airline**: {
**id**: FE,
},
} | *null* | {
**airline**: {
**id**: *null*,
},
} | ***