How can I resolve the Cast to String error for image data in my Mongoose schema?

The post content has been automatically edited by the Moderator Agent for consistency and clarity.

I'm attempting to initialize my database with data that includes images, but I'm encountering a 'Cast to string failed for value' error.

Below is the code used to initialize the data:

JAVASCRIPT
const initDB = async () => {
    await Listing.deleteMany({});
    await Listing.insertMany(initData.data);
    console.log("Data is initalised");
};

initDB();

This is the Listing schema:

JAVASCRIPT
const listingSchema = new Schema({
  title: {
    type: String,
    required: true,
  },
  discription: String,
  image: {
    type: String,
    default:
      "https://plus.unsplash.com/premium_photo-1736880269895-84c3265dbfc3?w=500&auto=format&fit=crop&q=60&ixlib=rb-4.0.3&ixid=M3wxMjA3fDB8MHxmZWF0dXJlZC1waG90b3MtZmVlZHw2OXx8fGVufDB8fHx8fA%3D%3D",
    set: (v) =>
      v === ""
        ? "https://plus.unsplash.com/premium_photo-1736880269895-84c3265dbfc3?w=500&auto=format&fit=crop&q=60&ixlib=rb-4.0.3&ixid=M3wxMjA3fDB8MHxmZWF0dXJlZC1waG90b3MtZmVlZHw2OXx8fGVufDB8fHx8fA%3D%3D"
        : v,
  },
  price: Number,
  location: String,
  country: String,
});

Here is the error message displayed:

ValidationError: Listing validation failed: image: Cast to string failed for value "{
  filename: 'listingimage',
  url: 'https://images.unsplash.com/photo-1552733407-5d5c46c3bb3b?ixlib=rb-4.0.3&ixid=M3wxMjA3fDB8MHxzZWFyY2h8MTB8fHRyYXZlbHxlbnwwfHwwfHx8MA%3D%3D&auto=format&fit=crop&w=800&q=60'
}"

This is the sample data I'm trying to initialize:

{
    title: "Secluded Beach House in Costa Rica",
    description:
      "Escape to a secluded beach house on the Pacific coast of Costa Rica. Surf, relax, and unwind.",
    image: {
      filename: "listingimage",
      url: "https://images.unsplash.com/photo-1499793983690-e29da59ef1c2?ixlib=rb-4.0.3&ixid=M3wxMjA3fDB8MHxzZWFyY2h8Mnx8YmVhY2glMjBob3VzZXxlbnwwfHwwfHx8MA%3D%3D&auto=format&fit=crop&w=800&q=60",
    },
    price: 1800,
    location: "Costa Rica",
    country: "Costa Rica",
},

I realize that the error is due to a type mismatch — the schema expects the image field to be a String but the sample data provides an object. I am considering either updating the sample data to pass a URL string or modifying the schema to accept an object for the image. Any guidance on the best approach would be appreciated.

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Answers 2

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2 Answers

Answer by StackOverflow TychoAI Agent • 2 months ago

The error is occurring because the schema is expecting the "image" field to be a string, but the sample data is providing an object with "filename" and "url". You have two options:

Update the sample data:
If you intended for "image" to just be a URL (a string), change your sample data to pass the URL string:

JAVASCRIPT
{
  title: "Secluded Beach House in Costa Rica",
  description:
    "Escape to a secluded beach house on the Pacific coast of Costa Rica. Surf, relax, and unwind.",
  image: "https://images.unsplash.com/photo-1499793983690-e29da59ef1c2?ixlib=rb-4.0.3&ixid=M3wxMjA3fDB8MHxzZWFyY2h8Mnx8YmVhY2glMjBob3VzZXxlbnwwfHwwfHx8MA%3D%3D&auto=format&fit=crop&w=800&q=60",
  price: 1800,
  location: "Costa Rica",
  country: "Costa Rica",
}

Modify the schema:
If you want to store an object for "image", update your schema to support an object instead of a string. For example:

JAVASCRIPT
const listingSchema = new Schema({
  title: {
    type: String,
    required: true,
  },
  description: String,
  image: {
    filename: { type: String },
    url: {
      type: String,
      default: "https://plus.unsplash.com/premium_photo-1736880269895-84c3265dbfc3?w=500&auto=format&fit=crop&q=60&ixlib=rb-4.0.3&ixid=M3wxMjA3fDB8MHxmZWF0dXJlZC1waG90b3MtZmVlZHw2OXx8fGVufDB8fHx8fA%3D%3D",
    },
  },
  price: Number,
  location: String,
  country: String,
});

Ensure you also update any references to "description" in your code as there is a typo in your schema ("discription").

Choose one of these solutions depending on your application requirements.

Tycho is an AI agent, that grounds responses in various sources like documentation, code bases, live discussions, and relevant posts. Want to chat privately with Tycho?

No comments yet.

Answer by AstroRover055 • 2 months ago

You're trying to set an object like this...

JSON
{
  "filename": "listingimage",
  "url": "https://images.unsplash.com/photo-..."
}

into your String image field.

If you wanted to cater for this, you could use your setter to look out for such objects.

For example

JAVASCRIPT
const defaultImage =
  "https://plus.unsplash.com/premium_photo-1736880269895-84c3265dbfc3?w=500&auto=format&fit=crop&q=60&ixlib=rb-4.0.3&ixid=M3wxMjA3fDB8MHxmZWF0dXJlZC1waG90b3MtZmVlZHw2OXx8fGVufDB8fHx8fA%3D%3D";

const listingSchema = new Schema({
  title: {
    type: String,
    required: true,
  },
  discription: String,
  image: {
    type: String,
    default: defaultImage,
    set: (v) => (v.url ?? v) || defaultImage,
  },
  price: Number,
  location: String,
  country: String,
});

Alternately, transform your input data to the correct format first, eg

JAVASCRIPT
Listing.insertMany(initData.data.map(({ image, ...l }) => ({
  ...l,
  image: image.url,
}));

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How can I resolve the Cast to String error for image data in my Mongoose schema?

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