ReadArrayWithType() (type)

Laurence MorganAbout 2 minAPI Reference

`ReadArrayWithType()` (type)

Read from a data type one array element at a time and return the elements contents and data type

Description

This is a function you would write when programming a Murex data-type.

It's called by builtins to allow them to read data structures one array element at a time.

The purpose of this function is to allow builtins to support sequential reads (where possible) and also create a standard interface for builtins, thus allowing them to be data-type agnostic.

This differs from ReadArray() because it also returns the data type.

There is a good chance ReadArray() might get deprecated in the medium to long term.

Usage

Registering your ReadArrayWithType()

// To avoid confusion, this should only happen inside func init()
stdio.RegisterReadArrayWithType(/* your type name */, /* your readArray func */)

Examples

Example ReadArrayWithType() function:

package string

import (
	"bufio"
	"context"
	"fmt"
	"strings"

	"github.com/lmorg/murex/lang/stdio"
	"github.com/lmorg/murex/lang/types"
)

func readArrayWithType(ctx context.Context, read stdio.Io, callback func(interface{}, string)) error {
	scanner := bufio.NewScanner(read)
	for scanner.Scan() {
		select {
		case <-ctx.Done():
			return scanner.Err()

		default:
			callback(strings.TrimSpace(scanner.Text()), types.String)
		}
	}

	err := scanner.Err()
	if err != nil {
		return fmt.Errorf("error while reading a %s array: %s", types.String, err.Error())
	}
	return nil
}

Detail

If your data type is not a stream-able array, it is then recommended that you pass your array to lang.ArrayWithTypeTemplate() which is a handler to convert Go structures into Murex arrays. This also makes writing ReadArray() handlers easier since you can just pass lang.ArrayTemplate() your marshaller. For example:

package json

import (
	"context"

	"github.com/lmorg/murex/lang"
	"github.com/lmorg/murex/lang/stdio"
	"github.com/lmorg/murex/lang/types"
	"github.com/lmorg/murex/utils/json"
)

func readArrayWithType(ctx context.Context, read stdio.Io, callback func(interface{}, string)) error {
	// Create a marshaller function to pass to ArrayWithTypeTemplate
	marshaller := func(v interface{}) ([]byte, error) {
		return json.Marshal(v, read.IsTTY())
	}

	return lang.ArrayWithTypeTemplate(ctx, types.Json, marshaller, json.Unmarshal, read, callback)
}

The downside of this is that you're then unmarshalling the entire file, which could be slow on large files and also breaks the streaming nature of UNIX pipelines.

Parameters

stdio.Io: stream to read from (eg stdin)
func(interface{}, string): callback function. Each callback will be the value in its native Go data type (eg string, int, float64, bool) for an array element

ReadArrayWithType() (type)

# ReadArrayWithType() (type)

# Description

# Usage

# Examples

# Detail

# Parameters

# See Also