Скачать или смотреть Resolving the unsupported data type: &[] Error in GORM with Custom Valuers

Discover how to fix the `unsupported data type: &[]` error in GORM when using a custom Valuer for a PostgreSQL model. Implement effective strategies for defining types and ensure smooth database integration.
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Resolving the unsupported data type: &[] Error in GORM with Custom Valuers

When working with GORM (a popular ORM for Go) and PostgreSQL, developers may run into the frustrating unsupported data type: &[] error, particularly when using custom types. This problem often arises when attempting to define a GORM model that includes a type with a custom Scanner and Valuer. If you've faced similar issues and are looking for a solution, you're in the right place!

Understanding the Problem

In this scenario, the developer is attempting to create a GORM model that contains a MultiString type, designed to hold a slice of strings. The goal is to store this string slice as a single column in the database. However, if the slice is empty or nil, the database column should also reflect that by being nil. Here is a simplified version of the code in question:

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When calling AutoMigrate on this struct, a unsupported data type: &[] error is thrown multiple times. This indicates that GORM is having difficulty discerning how to handle the custom data type.

Solution Strategies

To resolve this error, you have two effective strategies for defining your custom type in GORM. Let's explore them one by one.

1. Adding a Tag in the Model

One straightforward solution is to add the appropriate column type as a tag in your model. This approach is a common practice in GORM and ensures that the database column type is explicitly defined. Here's how you can modify your model:

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By specifying gorm:"type:text", you instruct GORM to use the text type for this column in the database. Keep in mind that you will need to apply this tag every time you use your new type in a model.

2. Implementing GORM Methods

Another effective approach is to implement GORM-specific methods on your custom data type. These methods inform GORM about the database type that should be used for your custom field. Here are the two methods you should implement:

GormDataType() string

GormDBDataType(db *gorm.DB, field *schema.Field) string

Here’s how you can define these methods for your custom MultiString type:

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These methods can be especially useful if you need to change the database type based on the type of database you are using.

Conclusion

By following either of the above strategies, you can eliminate the unsupported data type: &[] error and improve the compatibility of your custom build models with GORM. Whether you decide to use tags in your model or implement GORM-specific methods, both methods provide clarity and structure to your code, ensuring a smoother database interaction.

If you have any further questions or need clarification, feel free to ask in the comments below!