RoleResolverPower 场景

用一个 resolve 场景说明为什么某些点必须只有一个最终答案

场景

你希望某条链路里有人可以问：

  • “当前这个用户的角色是什么？”

这种问题不是多 Power 协同改值，而是必须有一个唯一答案。

这就是 resolve 的典型场景。

示例

import {
  Power,
  type PowerResolveHook,
} from "@downcity/city/power";

class RoleResolverPower extends Power {
  readonly name = "role_resolver";
  readonly title = "Role Resolver";
  readonly description = "Resolves one final role for a user.";

  private readonly resolveRole: PowerResolveHook = async ({ value }) => {
    const body = value as { userId?: unknown };
    const userId = String(body.userId || "").trim();
    if (!userId) {
      throw new Error("userId is required");
    }
    if (userId === "owner") return "admin";
    return "member";
  };

  readonly resolves = {
    "auth.resolve_role": this.resolveRole,
  };
}

// City 已登记并把 role_resolver 绑定到 entry 的 Agent/Workspace。
const role = await city.powers.scope({ agent_id: agent.id, workspace_id: workspace.id }).resolve<{ userId: string }, string>(
  "auth.resolve_role",
  { userId: "owner" },
);

为什么不能有两个 resolver

因为这类点的语义不是：

  • 大家都来补一点

而是：

  • 最终到底谁说了算

所以当前实现里，同一个 resolve 点重复注册会直接报错。

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