qparser is a simple package that help parse query parameters into struct in Go. It is inspired by gorilla/schema with main focus on query parameters. Built on top of Go stdlib, it uses custom struct tag qp to define the query parameter key .

Installation

go get -u github.com/prawirdani/qparser@latest

Example

Here's an example of how to use qparser to parse query parameters into struct.

// Representing basic pagination, /path?page=1&limit=5
type Pagination struct {
    Page    int `qp:"page"`
    Limit   int `qp:"limit"`
}

func MyHandler(w http.ResponseWriter, r *http.Request) {
    var pagination Pagination

    err := qparser.ParseRequest(r, &pagination)
    if err != nil {
        // Handle Error
    }
        
    // Do something with pagination
}

Multiple Values Query & Nested Struct

To support multiple values for a single query parameter, use a slice type. For nested structs, utilize the qp tag within the fields of the nested struct to pass the query parameters. It's important to note that the parent struct containing the nested/child struct should not have its own qp tag. Here's an example:

// Representing filter for menu
type MenuFilter struct {
    Categories []string `qp:"categories"`
    Available  bool     `qp:"available"`
}

type Pagination struct {
    Page    int `qp:"page"`
    Limit   int `qp:"limit"`
}

type MenuQueryParams struct {
    Filter     MenuFilter
    Pagination Pagination
}

func GetMenus(w http.ResponseWriter, r *http.Request) {
    var f MenuQueryParams
    if err := qparser.ParseRequest(r, &f); err != nil {
        // Handle Error
    }
    // Do something with f.Filter and f.Pagination
}

There are three ways for the parser to handle multiple values query parameters:

1. Comma-separated values: /menus?categories=desserts,beverages,sides
2. Repeated Keys: /menus?categories=desserts&categories=beverages&categories=sides
3. Combination of both: /menus?categories=desserts,beverages&categories=sides

Simply ensure that the qp tags are defined appropriately in your struct fields to map these parameters correctly.

Parse from URL

You can also parse query parameters from URL string by calling the ParseURL function. Here's an example:

func main() {
    var pagination Pagination

    url := "http://example.com/path?page=1&limit=5"

    err := qparser.ParseURL(url, &pagination)
    if err != nil {
        // Handle Error
    }

    // Do something with pagination
}

Notes

• Empty query values are not validated by default. For custom validation (including empty value checks), you can create your own validator by creating a pointer/value receiver method on the struct or with help of a third party validator package like go-playground/validator.
• Missing query parameters:
  • Primitive type fields keep their zero values (e.g., 0 for int, "" for string, false for bool)
  • Pointer fields are remain nil and slice are set to nil slice ([]).
  • A pointer nested struct will remain nil, only if all the fields are missing. If any field is present, the struct will be initialized and the missing fields will be set to their zero values.
• For multiple values query parameters, same value will be appended to the slice. If you want to make sure each value in the slice is unique, you can create a pointer receiver method on the struct to remove the duplicates or sanitize the values.
• The qp tag value is case-sensitive and must match the query parameter key exactly.

Supported field types

• String
• Boolean
• Integers (int, int8, int16, int32 and int64)
• Unsigned Integers (uint, uint8, uint16, uint32 and uint64)
• Floats (float64 and float32)
• Slice of above types
• Nested Struct
• A pointer to one of above

Future plans

• Introduce benchmarking to assess and optimize performance.
• Enhance overall performance and efficiency.
• Expand support to include various types, such as multidimensional slices and slices of structs, complex types, and more.
• Implement a default value mechanism for enhanced flexibility.
• Provide mapped errors for clearer error handling.
• Add support for custom multi-value separators.