fe-api

FE API Integration

$ARGUMENTS 를 분석하여 API 통합 레이어를 설계하거나 개선한다.

분석 절차

요구사항 파악: API 엔드포인트, 데이터 구조, 사용 패턴을 확인한다
기존 코드 분석: 프로젝트의 API 레이어 구조를 Glob/Read로 파악한다
패턴 제안: 최적의 데이터 페칭 전략을 제시한다
구현/개선: 승인 후 코드를 작성하거나 개선한다

API 클라이언트 설계

타입 안전한 Fetch Wrapper

// src/lib/api.ts import { z } from "zod";

class ApiError extends Error { constructor( public status: number, public statusText: string, public data?: unknown ) { super(API Error: ${status} ${statusText}); this.name = "ApiError"; } }

async function fetchApi<T>( url: string, schema: z.ZodType<T>, options?: RequestInit ): Promise<T> { const response = await fetch(url, { headers: { "Content-Type": "application/json", ...options?.headers }, ...options, });

if (!response.ok) { throw new ApiError(response.status, response.statusText); }

const data = await response.json(); return schema.parse(data); }

export { fetchApi, ApiError };

API 엔드포인트 정의

// src/lib/api/users.ts import { z } from "zod"; import { fetchApi } from "@/lib/api";

const userSchema = z.object({ id: z.string(), name: z.string(), email: z.string().email(), role: z.enum(["admin", "user"]), });

const usersResponseSchema = z.object({ data: z.array(userSchema), total: z.number(), });

type User = z.infer<typeof userSchema>;

async function getUsers(params?: { page?: number; limit?: number }) { const searchParams = new URLSearchParams(); if (params?.page) searchParams.set("page", String(params.page)); if (params?.limit) searchParams.set("limit", String(params.limit));

return fetchApi(/api/users?${searchParams}, usersResponseSchema); }

async function getUser(id: string) { return fetchApi(/api/users/${id}, userSchema); }

async function createUser(data: Omit<User, "id">) { return fetchApi(/api/users, userSchema, { method: "POST", body: JSON.stringify(data), }); }

export { getUsers, getUser, createUser }; export type { User };

TanStack Query 패턴

Query Key 관리

// src/lib/queryKeys.ts const queryKeys = { users: { all: ["users"] as const, lists: () => [...queryKeys.users.all, "list"] as const, list: (filters: Record<string, unknown>) => [...queryKeys.users.lists(), filters] as const, details: () => [...queryKeys.users.all, "detail"] as const, detail: (id: string) => [...queryKeys.users.details(), id] as const, }, products: { all: ["products"] as const, lists: () => [...queryKeys.products.all, "list"] as const, list: (filters: Record<string, unknown>) => [...queryKeys.products.lists(), filters] as const, details: () => [...queryKeys.products.all, "detail"] as const, detail: (id: string) => [...queryKeys.products.details(), id] as const, }, } as const;

export { queryKeys };

Query Hook

// src/hooks/useUsers.ts import { useQuery, useMutation, useQueryClient } from "@tanstack/react-query"; import { getUsers, getUser, createUser } from "@/lib/api/users"; import { queryKeys } from "@/lib/queryKeys";

function useUsers(filters?: { page?: number; limit?: number }) { return useQuery({ queryKey: queryKeys.users.list(filters ?? {}), queryFn: () => getUsers(filters), }); }

function useUser(id: string) { return useQuery({ queryKey: queryKeys.users.detail(id), queryFn: () => getUser(id), enabled: !!id, }); }

function useCreateUser() { const queryClient = useQueryClient();

return useMutation({ mutationFn: createUser, onSuccess: () => { queryClient.invalidateQueries({ queryKey: queryKeys.users.lists() }); }, }); }

export { useUsers, useUser, useCreateUser };

Optimistic Update

function useUpdateUser() { const queryClient = useQueryClient();

return useMutation({ mutationFn: updateUser, onMutate: async (newUser) => { await queryClient.cancelQueries({ queryKey: queryKeys.users.detail(newUser.id), });

  const previousUser = queryClient.getQueryData(
    queryKeys.users.detail(newUser.id)
  );

  queryClient.setQueryData(
    queryKeys.users.detail(newUser.id),
    newUser
  );

  return { previousUser };
},
onError: (_err, newUser, context) => {
  queryClient.setQueryData(
    queryKeys.users.detail(newUser.id),
    context?.previousUser
  );
},
onSettled: (_data, _err, newUser) => {
  queryClient.invalidateQueries({
    queryKey: queryKeys.users.detail(newUser.id),
  });
},

}); }

Infinite Query (무한 스크롤)

Prefetching

// Server Component에서 prefetch import { dehydrate, HydrationBoundary, QueryClient } from "@tanstack/react-query";

export default async function UsersPage() { const queryClient = new QueryClient();

await queryClient.prefetchQuery({ queryKey: queryKeys.users.list({}), queryFn: () => getUsers(), });

return ( <HydrationBoundary state={dehydrate(queryClient)}> <UserList /> </HydrationBoundary> ); }

Server Actions 패턴

기본 Server Action

// src/app/actions/users.ts "use server";

import { revalidatePath } from "next/cache"; import { z } from "zod";

const createUserSchema = z.object({ name: z.string().min(1, "이름을 입력하세요"), email: z.string().email("유효한 이메일을 입력하세요"), });

interface ActionState { success: boolean; message: string; errors?: Record<string, string[]>; }

async function createUserAction( _prevState: ActionState, formData: FormData ): Promise<ActionState> { const raw = { name: formData.get("name"), email: formData.get("email"), };

const result = createUserSchema.safeParse(raw);

if (!result.success) { return { success: false, message: "유효성 검사 실패", errors: result.error.flatten().fieldErrors, }; }

try { await db.user.create({ data: result.data }); revalidatePath("/users"); return { success: true, message: "사용자가 생성되었습니다" }; } catch (error) { return { success: false, message: "서버 오류가 발생했습니다" }; } }

export { createUserAction }; export type { ActionState };

useActionState로 폼 연동

"use client";

import { useActionState } from "react"; import { createUserAction } from "@/app/actions/users"; import type { ActionState } from "@/app/actions/users";

const initialState: ActionState = { success: false, message: "" };

function CreateUserForm() { const [state, formAction, isPending] = useActionState( createUserAction, initialState );

return ( <form action={formAction}> <Input name="name" placeholder="이름" /> {state.errors?.name && ( <p className="text-sm text-destructive">{state.errors.name[0]}</p> )}

  &#x3C;Input name="email" placeholder="이메일" type="email" />
  {state.errors?.email &#x26;&#x26; (
    &#x3C;p className="text-sm text-destructive">{state.errors.email[0]}&#x3C;/p>
  )}

  &#x3C;Button type="submit" disabled={isPending}>
    {isPending ? "생성 중..." : "생성"}
  &#x3C;/Button>

  {state.message &#x26;&#x26; (
    &#x3C;p className={state.success ? "text-green-600" : "text-destructive"}>
      {state.message}
    &#x3C;/p>
  )}
&#x3C;/form>

); }

API 에러 핸들링

전역 에러 핸들링 (QueryClient)

// src/lib/queryClient.ts import { QueryClient } from "@tanstack/react-query"; import { ApiError } from "@/lib/api";

export { makeQueryClient };

컴포넌트 레벨 에러 처리

function UserProfile({ id }: { id: string }) { const { data, error, isLoading } = useUser(id);

if (isLoading) return <Skeleton className="h-40 w-full" />;

if (error) { if (error instanceof ApiError && error.status === 404) { return <p>사용자를 찾을 수 없습니다.</p>; } return <p>데이터를 불러오는 중 오류가 발생했습니다.</p>; }

return <div>{data.name}</div>; }

Route Handler (API Route)

CRUD Route Handler

// src/app/api/users/route.ts import { NextRequest, NextResponse } from "next/server"; import { z } from "zod";

const createUserSchema = z.object({ name: z.string().min(1), email: z.string().email(), });

export async function GET(request: NextRequest) { const { searchParams } = request.nextUrl; const page = Number(searchParams.get("page") ?? "1"); const limit = Number(searchParams.get("limit") ?? "20");

const [users, total] = await Promise.all([ db.user.findMany({ skip: (page - 1) * limit, take: limit }), db.user.count(), ]);

return NextResponse.json({ data: users, total }); }

export async function POST(request: NextRequest) { const body = await request.json(); const result = createUserSchema.safeParse(body);

if (!result.success) { return NextResponse.json( { error: "Validation failed", details: result.error.flatten() }, { status: 400 } ); }

const user = await db.user.create({ data: result.data }); return NextResponse.json(user, { status: 201 }); }

동적 Route Handler

// src/app/api/users/[id]/route.ts import { NextRequest, NextResponse } from "next/server";

export async function GET( _request: NextRequest, { params }: { params: Promise<{ id: string }> } ) { const { id } = await params; const user = await db.user.findUnique({ where: { id } });

if (!user) { return NextResponse.json({ error: "Not found" }, { status: 404 }); }

return NextResponse.json(user); }

export async function PATCH( request: NextRequest, { params }: { params: Promise<{ id: string }> } ) { const { id } = await params; const body = await request.json(); const user = await db.user.update({ where: { id }, data: body }); return NextResponse.json(user); }

export async function DELETE( _request: NextRequest, { params }: { params: Promise<{ id: string }> } ) { const { id } = await params; await db.user.delete({ where: { id } }); return new NextResponse(null, { status: 204 }); }

MSW 개발용 Mock 서버

// src/mocks/handlers.ts import { http, HttpResponse } from "msw";

const users = [ { id: "1", name: "Alice", email: "alice@example.com", role: "admin" }, { id: "2", name: "Bob", email: "bob@example.com", role: "user" }, ];

export const handlers = [ http.get("/api/users", ({ request }) => { const url = new URL(request.url); const page = Number(url.searchParams.get("page") ?? "1"); const limit = Number(url.searchParams.get("limit") ?? "20"); const start = (page - 1) * limit;

return HttpResponse.json({
  data: users.slice(start, start + limit),
  total: users.length,
});

}),

http.post("/api/users", async ({ request }) => { const body = await request.json(); const newUser = { id: String(users.length + 1), ...body }; users.push(newUser); return HttpResponse.json(newUser, { status: 201 }); }), ];

실행 규칙

인자가 없으면 사용자에게 API 통합 대상을 질문한다
프로젝트의 기존 API 레이어를 먼저 파악한다 (lib/api, hooks, actions 등)
TanStack Query 사용 여부를 확인하고, 미설치 시 설치를 안내한다
Zod 스키마로 API 응답 타입을 검증하는 패턴을 기본으로 적용한다
Server Component에서의 데이터 페칭과 Client Component에서의 TanStack Query를 구분한다
에러 핸들링은 반드시 포함한다 (네트워크 에러, 유효성 에러, 서버 에러)

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