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Graph/dto-mapping-nested-types

Pattern

DTO Mapping For Nested Types

dto-mapping-nested-types

A recurring shape where response fields require a different type than the database model, so serialization/validation leaks nested objects and breaks the expected schema, and the fix is explicit DTO mapping or field-level transformation.

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Updated5/1/2026

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30 linked nodes

Type 'AccessorKeyColumnDef' is not assignable to type 'ColumnDef'. — while trying to create a column in `@tanstack/react-table`. Outcome: You can get rid of this TypeScript issue by casting the column definition arrays.

Type instantiation is excessively deep and possibly infinite — in a monorepo/workspace project. Tension: on seemingly benign types like this. Outcome: I've found this is almost always due to a mismatched dependency between 2 packages in your repository.

Normally, the response looks like this: — I have a model, called Candidate that I'm trying to return, two of the fields refer to another model, StaffMember. Tension: However, I don't want any nested fields.

that will give me 3 levels deep of nodes in my json output — I have a many to many self referential relationship. Tension: is there a way to do that so it goes as many levels deep as needed until nodes = [] ? Outcome: Do I need to use something like marshmallow-sqlalchemy ?

cannot adapt type 'dict' using placeholder '%s' (format: AUTO) — running query below query i'm getting error. Tension: I want check whether the particular email template is used in any other model instance and model Rule we have action(JSONB). Outcome: Rather than trying to construct a JSON literal in SQLAlchemy you could let Postgres do it using the `jsonb_build_object` function.

FastAPI cannot choose the correct model for a Union request body when one variant has an enum field

The `exclude_none` parameter to `model.model_dump` would apply to all entries of response, so it is not suitable. — Response is serialized/dumped as a JSON. Tension: I want attr2 to be included only if it is non-null. Importantly, `stuff1` should be included regardless of its type (null or int). Outcome: Pydantic v2 has custom serialization which allows one to control how objects are converted to JSON, but I am using 1.10.

SQLModel/Pydantic serializes the `categories: list[Category]` field as nested objects, but the API response needs `categories` as `list[str]` containing `Category.name` values.

I want to use Zod to validate dat — I'm building a Next.js application with TypeScript and Supabase as my backend. Tension: Supabase CLI automatically generates TypeScript types from my database schema. Outcome: This isn't ideal but has helped me and ensures that everything is typed which helps with the errors and maintenance.

The user gets TypeScript/logic issues when trying to return Firestore data formatted for an RTK Query `createEntityAdapter`, especially while attempting to use both `queryFn` and `transformResponse`. The endpoint also fails because `queryFn`/return shape expectations conflict with how `transformResponse` is meant to operate.

TypeScript type checking fails or behaves incorrectly when wiring Redux Toolkit `builder.addCase(...)` handlers for `findGoals` and `findSchedule`, especially around the `data` payload type and `action` typing.

There is no example on how to use enum mapping with postgres and hibernate 6. — I am migrating from hibernate 5 to 6. Tension: As @TypeDef is no more available I don't know how I can map my enum type to my database column.

I tried using `[key in FormData]:string`, but that forces me to have all fields, and not just one. Tension: I want to create a type that could encase the following: `{field1: string}` or `{field2: string}` and all other potential fields. Outcome: I don't want to make them all ignorable with `?`.

Trying to define a TypeScript type for a React function that accepts an object containing only one selected key from a larger object type (e.g., { field1: string } or { field2: string }) rather than all keys.

This only give me the Event type without the nested `Owner` property/relation. — I have a model with a relation to a separate model. I’m now querying the object and the related object. Tension: But how do I get a typescript type so that I can pass this object to subcomponents of my react component? Outcome: This only give me the Event type without the nested `Owner` property/relation.

TypeScript cannot infer the value type for a column accessor without passing the Row generic

the below post request is failing with the below exception — Spring Boot 4 project with the below controller and DTO.

it seems that is not working for me — Spring Data Couchbase and I have an entity that maps some of the fields of a document. Tension: I need all the other fields to be mapped to a Map<String, Object>.

After migrating from field injection to constructor-based injection, Spring throws a BeanCreationException when instantiating `exampleCommand` because it cannot resolve a constructor parameter for the DTO passed via `beanFactory.getBean(Command.class, inputDto)`.

as soon as I uncomment the line `@RequestBody UserDtoRequest userDtoRequest` and pass other data there with a name or email, I get a 403 error — I send the request via postman and form-data. Tension: I can only accept data from DTO if I use the raw data transfer format in Postman to JSON, but then I won't be able to attach an image. Outcome: send your data as form data along with the file.

I want map 1 field using several arguments, but not all arguments — @Mapping(target = "ss", source = ".", qualifiedByName = "sumThree"). Tension: Is it possible?

org.hibernate.query.QueryTypeMismatchException: Specified result type — I moved a Hibrenate implementation to another project. From com.mvc.data to com.mvc.frontend. Tension: Notice that it's the same type. Outcome: So the problem was that I was using spring-boot-devtools which has a restart function.

a fundamental property of value objects is that they should not be null — your `BankUpdateRequest`. Tension: which conflicts with the optional fields in your `BankUpdateRequest`. Outcome: allow `null` in DTOs.

I would like to use an existent Parent instance to create a child instance — with lombok Annotations. Tension: with all parent fields filled, and be able to complement with child properties. Outcome: instead of a parent's "field by field" solution.

there is some requirement where in particular 2-3 APIs, I dont want this prefix to come — We have used MappingJackson2HttpMessageConverter -> JsonPrefix to attach some prefix. Tension: This works corrects and provides response as expected. Outcome: So is there any way to achieve the same?

the `"type"` property is missing from the array elements in the obfuscated form — after running through ProGuard. Tension: This causes Jackson to deserialize those objects incorrectly. Outcome: allows the example to run successfully even after obfuscation.

A container entity needs to persist a List of objects whose types are subclasses of a common base class. Because the base is annotated with @MappedSuperclass, attempts to map the list using generics/relationship annotations fail.

{ "a": "this-is-ignored", "b": "uses-this-value" }. Tension: It works perfect when either `a` or `b` are present, and when both are present and `b` comes after `a`. Outcome: custom deserializer for whole class.

This works when I fetch into a record, but not my own pojo — I have tried many different variations including passing Long[].class to DSL.field. Tension: I just get the following. Outcome: please make sure it accommodates fetching multiple arrays of ids related to TEACHER with corresponding where/and clauses.

TS2353: Object literal may only specify known properties, and 'id' does not exist in type '[id: string, type: string, ...]' — The API serializer (graph.ts) used object literals typed as CompactNodeTuple/CompactEdgeTuple. Tension: tuples don't accept named object keys.

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