Resolving the error "Property not found on type 'any[]' after retrieving an object from the database in Typescript"

Question

Resolving the error "Property not found on type 'any[]' after retrieving an object from the database in Typescript"

Being a beginner in the world of TypeScript, I am struggling to comprehend the error message and how to resolve it.

This is the snippet of my code:

app.put('/compareSpread' , async (req , res) => {
  const { roundedSpreadPercentage , cropId} = req.body
  
  const crop = await CropInfo.find({entity: cropId})

  const diseaseSpreadOne = crop.diseaseSpreadOne
})

The error seems to be related to the line "const diseaseSpreadOne = crop.diseaseSpreadOne".

Here is a glimpse of what the database object looks like:

[
  {
    _id: new ObjectId("6349fbcde56e8b6b9dc94266"),
    entity: '64287197',
    diseaseName: 'Fungi',
    probability: 74.3,
    diseaseCause: null,
    ...
    image: 'https://plant.id/media/images/60e642b6cf4145739bde0c0947fcd933.jpg',
    plantTrue: 'true',
    is_healthy: 'false',
    healthyBoolean: false,
    dateTime: '2022-10-15',
    diseaseSpreadOne: 19.1,
    diseaseSpreadTwo: 19.1,
    __v: 0
  }
]

Even after receiving the above data from the database, I am still grappling with understanding the nature of the error.

typescript

Answer 1

Answer №1

An error message is displayed stating that "property does not exist on type any[]". When using the .find method, it returns an array which may not have the specified property. To resolve this issue, consider the following approach:

Remove the element from the array.

Specify the type as either 'any' or a custom type that includes the desired property.

You can do this by fetching data from the database and popping it out of the array, like so:

const crop = await CropInfo.find({ entity: cropId });
// Alternatively, use your own custom type
const obj = crop.pop() as any;
const diseaseSpreadOne = obj.diseaseSpreadOne;
// You can also define your own types in the model repository to ensure proper type inference when querying database.

Answer 2

An error message is displayed stating that "property does not exist on type any[]". When using the .find method, it returns an array which may not have the specified property. To resolve this issue, consider the following approach:

Remove the element from the array.

Specify the type as either 'any' or a custom type that includes the desired property.

You can do this by fetching data from the database and popping it out of the array, like so:

const crop = await CropInfo.find({ entity: cropId });
// Alternatively, use your own custom type
const obj = crop.pop() as any;
const diseaseSpreadOne = obj.diseaseSpreadOne;
// You can also define your own types in the model repository to ensure proper type inference when querying database.

Answer 3

Answer №2

If you want to ensure that the return value is an array of the specified type (CropInfo), you can utilize the as keyword.

interface CropInfo {
    entity: string;
    diseaseName: string;
    ...
    diseaseSpreadOne: number;
}

app.put('/compareSpread', async (req, res) => {
  const { roundedSpreadPercentage, cropId } = req.body;
  
  const crop = await CropInfo.find({ entity: cropId }) as CropInfo[];

  const diseaseSpreadOne = crop[0].diseaseSpreadOne;
})

Answer 4

If you want to ensure that the return value is an array of the specified type (CropInfo), you can utilize the as keyword.

interface CropInfo {
    entity: string;
    diseaseName: string;
    ...
    diseaseSpreadOne: number;
}

app.put('/compareSpread', async (req, res) => {
  const { roundedSpreadPercentage, cropId } = req.body;
  
  const crop = await CropInfo.find({ entity: cropId }) as CropInfo[];

  const diseaseSpreadOne = crop[0].diseaseSpreadOne;
})

Resolving the error "Property not found on type 'any[]' after retrieving an object from the database in Typescript"

Answer №1

Answer №2

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