go-conv: github.com/cstockton/go-conv Index | Examples | Files | Directories

package conv

import "github.com/cstockton/go-conv"

Package conv provides fast and intuitive conversions across Go types.

All conversion functions accept any type of value for conversion, if unable to find a reasonable conversion path they will return the target types zero value and an error.

Code:

// The zero value and a non-nil error is returned on failure.
fmt.Println(conv.Int("Foo"))

// Conversions are allowed as long as the underlying type is convertable, for
// example:
type MyString string
fmt.Println(conv.Int(MyString("42"))) // 42, nil

// Pointers will be dereferenced when appropriate.
str := "42"
fmt.Println(conv.Int(&str)) // 42, nil

// You may infer values from the base type of a pointer, giving you one
// function signature for all conversions. This may be convenient when the
// types are not known until runtime and reflection must be used.
var val int
err := conv.Infer(&val, `42`)
fmt.Println(val, err) // 42, nil

Output:

0 cannot convert "Foo" (type string) to int
42 <nil>
42 <nil>
42 <nil>

Numeric conversion from other numeric values of an identical type will be returned without modification. Numeric conversions deviate slightly from Go when dealing with under/over flow. When performing a conversion operation that would overflow, we instead assign the maximum value for the target type. Similarly, conversions that would underflow are assigned the minimun value for that type, meaning unsigned integers are given zero values instead of spilling into large positive integers.

Code:

// For more natural Float -> Integer when the underlying value is a string.
// Conversion functions will always try to parse the value as the target type
// first. If parsing fails float parsing with truncation will be attempted.
fmt.Println(conv.Int("-123.456")) // -123

// This does not apply for unsigned integers if the value is negative. Instead
// performing a more intuitive (to the human) truncation to zero.
fmt.Println(conv.Uint("-123.456")) // 0

Output:

-123 <nil>
0 <nil>

In short, panics should not occur within this library under any circumstance. This obviously excludes any oddities that may surface when the runtime is not in a healthy state, i.e. uderlying system instability, memory exhaustion. If you are able to create a reproducible panic please file a bug report.

Code:

// The zero value for the target type is always returned.
fmt.Println(conv.Bool(nil))
fmt.Println(conv.Bool([][]int{}))
fmt.Println(conv.Bool((chan string)(nil)))
fmt.Println(conv.Bool((*interface{})(nil)))
fmt.Println(conv.Bool((*interface{})(nil)))
fmt.Println(conv.Bool((**interface{})(nil)))

Output:

false cannot convert <nil> (type <nil>) to bool
false <nil>
false <nil>
false cannot convert (*interface {})(nil) (type *interface {}) to bool
false cannot convert (*interface {})(nil) (type *interface {}) to bool
false cannot convert (**interface {})(nil) (type **interface {}) to bool

Index

Examples

Package Files

conv.go

func Bool Uses

func Bool(from interface{}) (bool, error)

Bool will convert the given value to a bool, returns the default value of false if a conversion can not be made.

Bool conversion supports all the paths provided by the standard libraries strconv.ParseBool when converting from a string, all other conversions are simply true when not the types zero value. As a special case zero length map and slice types are also false, even if initialized.

Code:

// Bool conversion from other bool values will be returned without
// modification.
fmt.Println(conv.Bool(true))
fmt.Println(conv.Bool(false))

// Bool conversion from strings consider the following values true:
//   "t", "T", "true", "True", "TRUE",
// 	 "y", "Y", "yes", "Yes", "YES", "1"
//
// It considers the following values false:
//   "f", "F", "false", "False", "FALSE",
//   "n", "N", "no", "No", "NO", "0"
fmt.Println(conv.Bool("T"))
fmt.Println(conv.Bool("False"))

// Bool conversion from other supported types will return true unless it is
// the zero value for the given type.
fmt.Println(conv.Bool(int64(123)))
fmt.Println(conv.Bool(int64(0)))
fmt.Println(conv.Bool(time.Duration(123)))
fmt.Println(conv.Bool(time.Duration(0)))
fmt.Println(conv.Bool(time.Now()))
fmt.Println(conv.Bool(time.Time{}))

// All other types will return false.
fmt.Println(conv.Bool(struct{ string }{""}))

Output:

true <nil>
false <nil>
true <nil>
false <nil>
true <nil>
false <nil>
true <nil>
false <nil>
true <nil>
false <nil>
false cannot convert struct { string }{string:""} (type struct { string }) to bool

func Duration Uses

func Duration(from interface{}) (time.Duration, error)

Duration will convert the given value to a time.Duration, returns the default value of 0ns if a conversion can not be made.

Duration conversion supports all the paths provided by the standard libraries time.ParseDuration when converting from strings, with a couple enhancements outlined below.

Code:

// Duration conversion from strings will first attempt to parse as a Go
// duration value using ParseDuration, then fall back to numeric conventions.
fmt.Println(conv.Duration("1h1m100ms"))     // 1h1m0.1s
fmt.Println(conv.Duration("3660100000000")) // 1h1m0.1s

// Numeric conversions directly convert to time.Duration nanoseconds.
fmt.Println(conv.Duration(3660100000000)) // 1h1m0.1s

// Floats deviate from the numeric conversion rules, instead
// separating the integer and fractional portions into seconds.
fmt.Println(conv.Duration("3660.10"))        // 1h1m0.1s
fmt.Println(conv.Duration(float64(3660.10))) // 1h1m0.1s

// Complex numbers are Float conversions using the real number.
fmt.Println(conv.Duration(complex(3660.10, 0))) // 1h1m0.1s

// Duration conversion from time.Duration and any numerical type will be
// converted using a standard Go conversion. This includes strings
fmt.Println(conv.Duration(time.Nanosecond)) // 1s
fmt.Println(conv.Duration(byte(1)))         // 1ns

Output:

1h1m0.1s <nil>
1h1m0.1s <nil>
1h1m0.1s <nil>
1h1m0.1s <nil>
1h1m0.1s <nil>
1h1m0.1s <nil>
1ns <nil>
1ns <nil>

func Float32 Uses

func Float32(from interface{}) (float32, error)

Float32 will convert the given value to a float32, returns the default value of 0.0 if a conversion can not be made.

func Float64 Uses

func Float64(from interface{}) (float64, error)

Float64 will convert the given value to a float64, returns the default value of 0.0 if a conversion can not be made.

Float64 conversion from other float values of an identical type will be returned without modification. Float64 from other types follow the general numeric rules.

Code:

fmt.Println(conv.Float64(float64(123.456))) // 123.456
fmt.Println(conv.Float64("-123.456"))       // -123.456
fmt.Println(conv.Float64("1.7976931348623157e+308"))

Output:

123.456 <nil>
-123.456 <nil>
1.7976931348623157e+308 <nil>

func Infer Uses

func Infer(into, from interface{}) error

Infer will perform conversion by inferring the conversion operation from the base type of a pointer to a supported T.

Example:

var into int64
err := conv.Infer(&into, `12`)
// into -> 12

See examples for more usages.

Infer will perform conversion by inferring the conversion operation from a pointer to a supported T of the `into` param. Since the value is assigned directly only a error value is returned, meaning no type assertions needed.

Code:

// Infer requires a pointer to all types.
var into int
if err := conv.Infer(into, `42`); err != nil {
    fmt.Println(err)
}
if err := conv.Infer(&into, `42`); err == nil {
    fmt.Println(into)
}

// Same as above but using new()
truth := new(bool)
if err := conv.Infer(truth, `TRUE`); err != nil {
    fmt.Println("Failed!")
}

Output:

cannot infer conversion for unchangeable 0 (type int)
42

func Int Uses

func Int(from interface{}) (int, error)

Int will convert the given value to a int, returns the default value of 0 if a conversion can not be made.

Int conversions follow the the general numeric rules.

Code:

fmt.Println(conv.Uint("123.456"))               // 123
fmt.Println(conv.Uint("-123.456"))              // 0
fmt.Println(conv.Uint8(uint64(math.MaxUint64))) // 255

Output:

123 <nil>
0 <nil>
255 <nil>

func Int16 Uses

func Int16(from interface{}) (int16, error)

Int16 will convert the given value to a int16, returns the default value of 0 if a conversion can not be made.

func Int32 Uses

func Int32(from interface{}) (int32, error)

Int32 will convert the given value to a int32, returns the default value of 0 if a conversion can not be made.

func Int64 Uses

func Int64(from interface{}) (int64, error)

Int64 will convert the given value to a int64, returns the default value of 0 if a conversion can not be made.

func Int8 Uses

func Int8(from interface{}) (int8, error)

Int8 will convert the given value to a int8, returns the default value of 0 if a conversion can not be made.

func String Uses

func String(from interface{}) (string, error)

String will convert the given value to a string, returns the default value of "" if a conversion can not be made.

String conversion from any values outside the cases below will simply be the result of calling fmt.Sprintf("%v", value), meaning it can not fail. An error is still provided and you should check it to be future proof.

Code:

// String conversion from other string values will be returned without
// modification.
fmt.Println(conv.String("Foo"))

// As a special case []byte will also be returned after a Go string conversion
// is applied.
fmt.Println(conv.String([]byte("Foo")))

// String conversion from types that do not have a valid conversion path will
// still have sane string conversion for troubleshooting.
fmt.Println(conv.String(struct{ msg string }{"Foo"}))

Output:

Foo <nil>
Foo <nil>
{Foo} <nil>

func Time Uses

func Time(from interface{}) (time.Time, error)

Time will convert the given value to a time.Time, returns the empty struct time.Time{} if a conversion can not be made.

Time conversion from other time values will be returned without modification.

Code:

// Time conversion from other time.Time values will be returned without
// modification.
fmt.Println(`Times:`)
fmt.Println(conv.Time(time.Date(2006, 1, 2, 15, 4, 5, 0, time.UTC)))

// Time conversion from strings will be passed through time.Parse using a
// variety of formats. Strings that could not be parsed along with all other
// values will return an empty time.Time{} struct.
fmt.Println(`Strings:`)
formats := []string{
    `Mon, 02 Jan 2006 15:04:05`,
    `Mon, 02 Jan 2006 15:04:05 UTC`,
    `Mon, 2 Jan 2006 15:04:05`,
    `Mon, 2 Jan 2006 15:04:05 UTC`,
    `02 Jan 2006 15:04 UTC`,
    `2 Jan 2006 15:04:05`,
    `2 Jan 2006 15:04:05 UTC`,
}
for _, format := range formats {
    t, err := conv.Time(format)
    if err != nil {
        fmt.Println(`Conversion error: `, err)
    }
    fmt.Printf("%v <-- (%v)\n", t, format)
}

// Time conversion from types that do not have a valid conversion path will
// return the zero value and an error.
fmt.Println(`Errors:`)
fmt.Println(conv.Time(1))    // cannot convert 1 (type int) to time.Time
fmt.Println(conv.Time(true)) // cannot convert true (type bool) to time.Time

Output:

Times:
2006-01-02 15:04:05 +0000 UTC <nil>
Strings:
2006-01-02 15:04:05 +0000 UTC <-- (Mon, 02 Jan 2006 15:04:05)
2006-01-02 15:04:05 +0000 UTC <-- (Mon, 02 Jan 2006 15:04:05 UTC)
2006-01-02 15:04:05 +0000 UTC <-- (Mon, 2 Jan 2006 15:04:05)
2006-01-02 15:04:05 +0000 UTC <-- (Mon, 2 Jan 2006 15:04:05 UTC)
2006-01-02 15:04:00 +0000 UTC <-- (02 Jan 2006 15:04 UTC)
2006-01-02 15:04:05 +0000 UTC <-- (2 Jan 2006 15:04:05)
2006-01-02 15:04:05 +0000 UTC <-- (2 Jan 2006 15:04:05 UTC)
Errors:
0001-01-01 00:00:00 +0000 UTC cannot convert 1 (type int) to time.Time
0001-01-01 00:00:00 +0000 UTC cannot convert true (type bool) to time.Time

func Uint Uses

func Uint(from interface{}) (uint, error)

Uint will convert the given value to a uint, returns the default value of 0 if a conversion can not be made.

Uint conversions follow the the general numeric rules.

Code:

fmt.Println(conv.Uint("123.456"))               // 123
fmt.Println(conv.Uint("-123.456"))              // 0
fmt.Println(conv.Uint8(uint64(math.MaxUint64))) // 255

Output:

123 <nil>
0 <nil>
255 <nil>

func Uint16 Uses

func Uint16(from interface{}) (uint16, error)

Uint16 will convert the given value to a uint16, returns the default value of 0 if a conversion can not be made.

func Uint32 Uses

func Uint32(from interface{}) (uint32, error)

Uint32 will convert the given value to a uint32, returns the default value of 0 if a conversion can not be made.

func Uint64 Uses

func Uint64(from interface{}) (uint64, error)

Uint64 will convert the given value to a uint64, returns the default value of 0 if a conversion can not be made.

func Uint8 Uses

func Uint8(from interface{}) (uint8, error)

Uint8 will convert the given value to a uint8, returns the default value of 0 if a conversion can not be made.

Directories

PathSynopsis
internal/convertPackage convert contains common conversion interfaces.
internal/generated
internal/refconvPackage refconv implements the Converter interface by using the standard libraries reflection package.
internal/refutil
internal/testconv

Package conv imports 2 packages (graph) and is imported by 6 packages. Updated 2018-02-24. Refresh now. Tools for package owners.