Promise 参数类型不可分配

Question

I have the following method on an Angular component class:

getPluginViaUrl(url: string): Promise<SCEPluginElement | string> {

    const self = this;

    return fetch(url, {cache: 'no-store'}).then(function (result) {
        return result.text();
      })
      .then(function (code) {

        const result = self.evalPluginCode(code);

        if (!result.SCEPlugin) {
          return Promise.reject('No SCEPlugin property exported from supposed plugin.');
        }

        if (!result.SCEPlugin.pluginName) {
          return Promise.reject('SCEPlugin is missing a name (missing "pluginName" field)');
        }

        if (!result.SCEPlugin.pluginType) {
          return Promise.reject('SCEPlugin is missing a type (missing "pluginType" field).');
        }


        return {
          url: url,
          code: code,
          pluginName: result.SCEPlugin.pluginName,
          pluginType: result.SCEPlugin.pluginType,
          plugin: result.SCEPlugin
        };

      });
  }

here is the type being used:

export interface SCEPluginElement {
  url: string,
  code: string,
  pluginName: string,
  pluginType: string,
  plugin: Object
}

but I am getting this error:

ERROR in src/app/shared/services/utils-service.ts(57,13): error TS2345: Argument of type '(code: string) => Promise | { url: string; code: string; pluginName: any; pluginType: any;...' is not assignable to parameter of type '(value: string) => PromiseLike'. Type 'Promise | { url: string; code: string; pluginName: any; pluginType: any; plugin: any; }' is not assignable to type 'PromiseLike'. Type '{ url: string; code: string; pluginName: any; pluginType: any; plugin: any; }' is not assignable to type 'PromiseLike'. Property 'then' is missing in type '{ url: string; code: string; pluginName: any; pluginType: any; plugin: any; }'.

I cannot figure out what this error means.

Answer 1

You're receiving this error because you are returning Promise s for your errors and not string s.

I'd suggest replacing all return new Promise with throw new Error . Then you can use .catch to handle the errors and simply return a SCEPluginElement instead of SCEPluginElement | string SCEPluginElement | string .