CODEWITHSUNDEEP
typescript
programmer
programmer

Reputation: 770

How to use interface for nested functions

I don't know how to set the correct topic for my question, so if someone has a better name, please edit me :)

The subject is:

I have 2 functions that use the same interface:

interface createMailInterface {
  to: String,
  subject: String,
  message: String
}

const createMail = (config: createMailInterface) => {
  const {to, subject, message} = config
  const mailOptions = {
    from: process.env.MAIL_USER_NAME,
    to,
    subject,
    message
  }

  return mailOptions
}


const sendMail = (config: createMailInterface): void => {

  transporter.sendMail( createMail(config), (error, info) => {
    if (error) {
      logger.error(error)
    } else {
      logger.info(`Email sent: ${info.response}`)
    }
  })
}

But in declaration on sendMail function I have a warning like:

Argument of type '{ from: string | undefined; to: String; subject: String; message: String; }' is not assignable to parameter of type 'Options'.

in place: createMail(config)

So my question is, how can I use the same interface for nested functions like in the example above?

Upvotes: 0

Views: 281

Answers (1)

David Ko
David Ko

Reputation: 189

It looks like your transporter.sendMail method has it's own interface defined called 'Options'. You can see the type definition by command/control clicking on the transporter.sendMail method.

I'm guessing the interface is something like this.

interface Options {
from: string
to: string
subject: string
}

In your case, your "from" variable can be string or undefined because process.env.MAIL_USER_NAME can theoretically be undefined, so you can have an

if(process.env.MAIL_USER_NAME){
 ** Run code here **
}

or an

if(!process.env.MAIL_USER_NAME){
** Handle your error **
}

To make sure it is never undefined, for the "to" and "subject" variables, just change your "String" in your interface to "string".

Upvotes: 1

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