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How to Resolve the 'json: cannot unmarshal array into Go value' Error?

Mary-Kate Olsen
Mary-Kate OlsenOriginal
2024-12-04 18:53:11782browse

How to Resolve the

Unraveling the "Cannot Unmarshal Array into Go Value" Conundrum

Understanding the Issue:

While attempting to parse data from a JSON API, an unexpected error arises: "panic: json: cannot unmarshal array into Go value of type main.Structure." This error indicates a mismatch between the JSON data and the Go structure defined.

Identifying the Discrepancy:

Upon examining the code, it becomes apparent that the Structure type expects an array of interface{} objects as its 'stuff' field. However, the JSON data being parsed is an array itself, not an array of interface{} objects.

Solution 1: Unmarshal to a Slice

To resolve the mismatch, it's recommended to unmarshal the JSON array to a slice of interface{} objects instead. This way, the JSON array structure is preserved within the Go code:

var data []interface{}
err = json.Unmarshal(body, &data)

Solution 2: Define Specific Struct Fields

Alternatively, if the JSON response data has a consistent structure, consider defining a Go struct that matches the exact fields present in the response. This allows for a more structured and type-safe unmarshalling process:

type Tick struct {
     ID string
     Name string
     Symbol string
     Rank string
     Price_USD string
     ... and so on
}

var data []Tick
err = json.Unmarshal(body, &data)

By employing either of these approaches, the application can successfully parse the JSON data and avoid the "cannot unmarshal array into Go value" error.

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