TypeScript：返回类型取决于参数

大佬教程收集整理的这篇文章主要介绍了TypeScript：返回类型取决于参数，大佬教程大佬觉得挺不错的，现在分享给大家，也给大家做个参考。

如何解决TypeScript：返回类型取决于参数？

开发过程中遇到TypeScript：返回类型取决于参数的问题如何解决？下面主要结合日常开发的经验，给出你关于TypeScript：返回类型取决于参数的解决方法建议，希望对你解决TypeScript：返回类型取决于参数有所启发或帮助；

我有以下 TypeScript 函数：

declare function getUserContext(
  options: UserContextoptions
): Promise<UserContext>;

declare function getTeamContext(
  options: TeamContextoptions
): Promise<TeamContext>;

type UserContextWithoutSlackTeamOptions = Omit<
  UserContextoptions,'slackTeamRef'
>;

async function getContext<
  T extends
    | TeamContextoptions
    | (TeamContextoptions & UserContextWithoutSlackTeamOptions)
>(
  options: Partial<UserContextWithoutSlackTeamOptions> & T
): Promise<
  T extends UserContextWithoutSlackTeamOptions
    ? TeamContext & UserContext
    : TeamContext
> {
  const teamContext = await getTeamContext(options);
  const userContext = optionS.User
    ? await getUserContext({
        user: optionS.User,slackTeamRef: teamContext.slackTeam,})
    : undefined;

  return {
    ...teamContext,...userContext,octokit: userContext.octokit ?? teamContext.octokit,};
}

这里是接口：

interface UserContextoptions {
  user: {
    ID: String;
    name?: String;
  };
  slackTeamRef: String;
}

interface TeamContextoptions {
  teamID: String;
}

interface TeamContext {
  slackTeam: String;
  octokit: String;
}

interface UserContext {
  user: String | null | undefined;
  slackUser: String;
  octokit: String | undefined;
}

从逻辑上讲，我认为这会起作用，但是 TypeScript 在几个地方抱怨：

在 return 语句中，它说

TS2322: Type '{ octokit: String; user?: String | null | undefined; slackUser?: String | undefined; slackTeam: String; }' is not assignable to type 'TeamContext & UserContext'.  
 Type '{ octokit: String; user?: String | null | undefined; slackUser?: String | undefined; slackTeam: String; }' is not assignable to type 'UserContext'.    
 Property 'user' is optional in type '{ octokit: String; user?: String | null | undefined; slackUser?: String | undefined; slackTeam: String; }' but required in type 'UserContext'.

TS2532: Object is possibly 'undefined'.

我查看了许多其他 SO 帖子，但我遇到的任何解决方案都不适用于此特定场景。

感谢任何帮助，谢谢。

TS Playground

解决方法

@H_696_32@

Function Overloads 就是为此而设计的

async function getContext(options: TeamContextOptions & UserContextWithoutSlackTeamOptions): Promise<TeamContext & UserContext>;
async function getContext(options: TeamContextOptions): Promise<TeamContext>;
async function getContext(
  options: TeamContextOptions & UserContextWithoutSlackTeamOptions | TeamContextOptions & Partial<UserContextWithoutSlackTeamOptions>
) {
  // impl...
}

declare const teamOption: TeamContextOptions
declare const mixOption: TeamContextOptions & UserContextWithoutSlackTeamOptions

async () => {
  const v1 = await getContext(teamOption) // TeamContext
  const v2 = await getContext(mixOption) // TeamContext & UserContext
}