Documentation
¶
Index ¶
- Constants
- type ChanDir
- type Kind
- type SliceHeader
- type StructField
- type StructTag
- type Type
- type Value
- func (v Value) Bytes() []byte
- func (v Value) CanAddr() bool
- func (v Value) CanConvert(t Type) bool
- func (v Value) CanConvertWithInterface(t Type) bool
- func (v Value) CanSet() bool
- func (v Value) Complex() complex128
- func (v Value) Convert(t Type) Value
- func (v Value) ConvertWithInterface(t Type) Value
- func (v Value) Elem() Value
- func (v Value) Field(i int) Value
- func (v Value) Float() float64
- func (v Value) Index(i int) Value
- func (v Value) Int() int64
- func (v Value) Interface() (i interface{})
- func (v Value) IsNil() bool
- func (v Value) IsValid() bool
- func (v Value) Kind() Kind
- func (v Value) Len() int
- func (v Value) MapIndex(key Value) Value
- func (v Value) MapKeys() []Value
- func (v Value) NumField() int
- func (v Value) NumMethod() int
- func (v Value) Pointer() uintptr
- func (v Value) Set(x Value)
- func (v Value) SetBytes(x []byte)
- func (v Value) SetMapIndex(key, elem Value)
- func (v Value) SetPointer(x unsafe.Pointer)
- func (v Value) SetString(x string)
- func (v Value) String() string
- func (v Value) Type() Type
- func (v Value) Uint() uint64
- func (v Value) UnsafeAddr() uintptr
- type ValueError
Constants ¶
const Ptr = Pointer
Ptr is the old name for the Pointer kind.
Variables ¶
This section is empty.
Functions ¶
This section is empty.
Types ¶
type Kind ¶
type Kind uint
A Kind represents the specific kind of type that a Type represents. The zero Kind is not a valid kind.
type SliceHeader ¶
SliceHeader is the runtime representation of a slice. It cannot be used safely or portably and its representation may change in a later release. Moreover, the Data field is not sufficient to guarantee the data it references will not be garbage collected, so programs must keep a separate, correctly typed pointer to the underlying data.
type StructField ¶
type StructField struct {
// Name is the field name.
Name string
// PkgPath is the package path that qualifies a lower case (unexported)
// field name. It is empty for upper case (exported) field names.
// See https://golang.org/ref/spec#Uniqueness_of_identifiers
PkgPath string
Type Type // field type
Tag StructTag // field tag string
Offset uintptr // offset within struct, in bytes
Index []int // index sequence for Type.FieldByIndex
Anonymous bool // is an embedded field
}
A StructField describes a single field in a struct.
type Type ¶
type Type interface {
// NumMethod returns the number of methods accessible using Method.
//
// For a non-interface type, it returns the number of exported methods.
//
// For an interface type, it returns the number of exported and unexported methods.
NumMethod() int
// Name returns the type's name within its package for a defined type.
// For other (non-defined) types it returns the empty string.
Name() string
// PkgPath returns a defined type's package path, that is, the import path
// that uniquely identifies the package, such as "encoding/base64".
// If the type was predeclared (string, error) or not defined (*T, struct{},
// []int, or A where A is an alias for a non-defined type), the package path
// will be the empty string.
PkgPath() string
// String returns a string representation of the type.
// The string representation may use shortened package names
// (e.g., base64 instead of "encoding/base64") and is not
// guaranteed to be unique among types. To test for type identity,
// compare the Types directly.
String() string
// Kind returns the specific kind of this type.
Kind() Kind
// ConvertibleTo reports whether a value of the type is convertible to type u.
// Even if ConvertibleTo returns true, the conversion may still panic.
// For example, a slice of type []T is convertible to *[N]T,
// but the conversion will panic if its length is less than N.
ConvertibleTo(u Type) bool
ConvertibleToWithInterface(u Type) bool
// ChanDir returns a channel type's direction.
// It panics if the type's Kind is not Chan.
ChanDir() ChanDir
// IsVariadic reports whether a function type's final input parameter
// is a "..." parameter. If so, t.In(t.NumIn() - 1) returns the parameter's
// implicit actual type []T.
//
// For concreteness, if t represents func(x int, y ... float64), then
//
// t.NumIn() == 2
// t.In(0) is the reflect.Type for "int"
// t.In(1) is the reflect.Type for "[]float64"
// t.IsVariadic() == true
//
// IsVariadic panics if the type's Kind is not Func.
IsVariadic() bool
// Elem returns a type's element type.
// It panics if the type's Kind is not Array, Chan, Map, Pointer, or Slice.
Elem() Type
// Field returns a struct type's i'th field.
// It panics if the type's Kind is not Struct.
// It panics if i is not in the range [0, NumField()).
Field(i int) StructField
// In returns the type of a function type's i'th input parameter.
// It panics if the type's Kind is not Func.
// It panics if i is not in the range [0, NumIn()).
In(i int) Type
// Key returns a map type's key type.
// It panics if the type's Kind is not Map.
Key() Type
// Len returns an array type's length.
// It panics if the type's Kind is not Array.
Len() int
// NumField returns a struct type's field count.
// It panics if the type's Kind is not Struct.
NumField() int
// NumIn returns a function type's input parameter count.
// It panics if the type's Kind is not Func.
NumIn() int
// NumOut returns a function type's output parameter count.
// It panics if the type's Kind is not Func.
NumOut() int
// Out returns the type of a function type's i'th output parameter.
// It panics if the type's Kind is not Func.
// It panics if i is not in the range [0, NumOut()).
Out(i int) Type
// contains filtered or unexported methods
}
Type is the representation of a Go type.
Not all methods apply to all kinds of types. Restrictions, if any, are noted in the documentation for each method. Use the Kind method to find out the kind of type before calling kind-specific methods. Calling a method inappropriate to the kind of type causes a run-time panic.
Type values are comparable, such as with the == operator, so they can be used as map keys. Two Type values are equal if they represent identical types.
type Value ¶
type Value struct {
// contains filtered or unexported fields
}
Value is the reflection interface to a Go value.
Not all methods apply to all kinds of values. Restrictions, if any, are noted in the documentation for each method. Use the Kind method to find out the kind of value before calling kind-specific methods. Calling a method inappropriate to the kind of type causes a run time panic.
The zero Value represents no value. Its IsValid method returns false, its Kind method returns Invalid, its String method returns "<invalid Value>", and all other methods panic. Most functions and methods never return an invalid value. If one does, its documentation states the conditions explicitly.
A Value can be used concurrently by multiple goroutines provided that the underlying Go value can be used concurrently for the equivalent direct operations.
To compare two Values, compare the results of the Interface method. Using == on two Values does not compare the underlying values they represent.
func Indirect ¶
Indirect returns the value that v points to. If v is a nil pointer, Indirect returns a zero Value. If v is not a pointer, Indirect returns v.
func MakeMapWithSize ¶
MakeMapWithSize creates a new map with the specified type and initial space for approximately n elements.
func New ¶
New returns a Value representing a pointer to a new zero value for the specified type. That is, the returned Value's Type is PointerTo(typ).
func NewAt ¶
NewAt returns a Value representing a pointer to a value of the specified type, using p as that pointer.
func ValueOf ¶
func ValueOf(i interface{}) Value
ValueOf returns a new Value initialized to the concrete value stored in the interface i. ValueOf(nil) returns the zero Value.
func Zero ¶
Zero returns a Value representing the zero value for the specified type. The result is different from the zero value of the Value struct, which represents no value at all. For example, Zero(TypeOf(42)) returns a Value with Kind Int and value 0. The returned value is neither addressable nor settable.
func (Value) Bytes ¶
Bytes returns v's underlying value. It panics if v's underlying value is not a slice of bytes or an addressable array of bytes.
func (Value) CanAddr ¶
CanAddr reports whether the value's address can be obtained with Addr. Such values are called addressable. A value is addressable if it is an element of a slice, an element of an addressable array, a field of an addressable struct, or the result of dereferencing a pointer. If CanAddr returns false, calling Addr will panic.
func (Value) CanConvert ¶
CanConvert reports whether the value v can be converted to type t. If v.CanConvert(t) returns true then v.Convert(t) will not panic.
func (Value) CanConvertWithInterface ¶
func (Value) CanSet ¶
CanSet reports whether the value of v can be changed. A Value can be changed only if it is addressable and was not obtained by the use of unexported struct fields. If CanSet returns false, calling Set or any type-specific setter (e.g., SetBool, SetInt) will panic.
func (Value) Complex ¶
func (v Value) Complex() complex128
Complex returns v's underlying value, as a complex128. It panics if v's Kind is not Complex64 or Complex128
func (Value) Convert ¶
Convert returns the value v converted to type t. If the usual Go conversion rules do not allow conversion of the value v to type t, or if converting v to type t panics, Convert panics.
func (Value) ConvertWithInterface ¶
func (Value) Elem ¶
Elem returns the value that the interface v contains or that the pointer v points to. It panics if v's Kind is not Interface or Pointer. It returns the zero Value if v is nil.
func (Value) Field ¶
Field returns the i'th field of the struct v. It panics if v's Kind is not Struct or i is out of range.
func (Value) Float ¶
Float returns v's underlying value, as a float64. It panics if v's Kind is not Float32 or Float64
func (Value) Index ¶
Index returns v's i'th element. It panics if v's Kind is not Array, Slice, or String or i is out of range.
func (Value) Int ¶
Int returns v's underlying value, as an int64. It panics if v's Kind is not Int, Int8, Int16, Int32, or Int64.
func (Value) Interface ¶
func (v Value) Interface() (i interface{})
Interface returns v's current value as an interface{}. It is equivalent to:
var i interface{} = (v's underlying value)
It panics if the Value was obtained by accessing unexported struct fields.
func (Value) IsNil ¶
IsNil reports whether its argument v is nil. The argument must be a chan, func, interface, map, pointer, or slice value; if it is not, IsNil panics. Note that IsNil is not always equivalent to a regular comparison with nil in Go. For example, if v was created by calling ValueOf with an uninitialized interface variable i, i==nil will be true but v.IsNil will panic as v will be the zero Value.
func (Value) IsValid ¶
IsValid reports whether v represents a value. It returns false if v is the zero Value. If IsValid returns false, all other methods except String panic. Most functions and methods never return an invalid Value. If one does, its documentation states the conditions explicitly.
func (Value) Kind ¶
Kind returns v's Kind. If v is the zero Value (IsValid returns false), Kind returns Invalid.
func (Value) Len ¶
Len returns v's length. It panics if v's Kind is not Array, Chan, Map, Slice, String, or pointer to Array.
func (Value) MapIndex ¶
MapIndex returns the value associated with key in the map v. It panics if v's Kind is not Map. It returns the zero Value if key is not found in the map or if v represents a nil map. As in Go, the key's value must be assignable to the map's key type.
func (Value) MapKeys ¶
MapKeys returns a slice containing all the keys present in the map, in unspecified order. It panics if v's Kind is not Map. It returns an empty slice if v represents a nil map.
func (Value) NumField ¶
NumField returns the number of fields in the struct v. It panics if v's Kind is not Struct.
func (Value) NumMethod ¶
NumMethod returns the number of methods in the value's method set.
For a non-interface type, it returns the number of exported methods.
For an interface type, it returns the number of exported and unexported methods.
func (Value) Pointer ¶
Pointer returns v's value as a uintptr. It returns uintptr instead of unsafe.Pointer so that code using reflect cannot obtain unsafe.Pointers without importing the unsafe package explicitly. It panics if v's Kind is not Chan, Func, Map, Pointer, Slice, or UnsafePointer.
If v's Kind is Func, the returned pointer is an underlying code pointer, but not necessarily enough to identify a single function uniquely. The only guarantee is that the result is zero if and only if v is a nil func Value.
If v's Kind is Slice, the returned pointer is to the first element of the slice. If the slice is nil the returned value is 0. If the slice is empty but non-nil the return value is non-zero.
It's preferred to use uintptr(Value.UnsafePointer()) to get the equivalent result.
func (Value) Set ¶
Set assigns x to the value v. It panics if CanSet returns false. As in Go, x's value must be assignable to v's type.
func (Value) SetBytes ¶
SetBytes sets v's underlying value. It panics if v's underlying value is not a slice of bytes.
func (Value) SetMapIndex ¶
SetMapIndex sets the element associated with key in the map v to elem. It panics if v's Kind is not Map. If elem is the zero Value, SetMapIndex deletes the key from the map. Otherwise if v holds a nil map, SetMapIndex will panic. As in Go, key's elem must be assignable to the map's key type, and elem's value must be assignable to the map's elem type.
func (Value) SetPointer ¶
SetPointer sets the unsafe.Pointer value v to x. It panics if v's Kind is not UnsafePointer.
func (Value) SetString ¶
SetString sets v's underlying value to x. It panics if v's Kind is not String or if CanSet() is false.
func (Value) String ¶
String returns the string v's underlying value, as a string. String is a special case because of Go's String method convention. Unlike the other getters, it does not panic if v's Kind is not String. Instead, it returns a string of the form "<T value>" where T is v's type. The fmt package treats Values specially. It does not call their String method implicitly but instead prints the concrete values they hold.
func (Value) Uint ¶
Uint returns v's underlying value, as a uint64. It panics if v's Kind is not Uint, Uintptr, Uint8, Uint16, Uint32, or Uint64.
func (Value) UnsafeAddr ¶
UnsafeAddr returns a pointer to v's data, as a uintptr. It is for advanced clients that also import the "unsafe" package. It panics if v is not addressable.
It's preferred to use uintptr(Value.Addr().UnsafePointer()) to get the equivalent result.
type ValueError ¶
A ValueError occurs when a Value method is invoked on a Value that does not support it. Such cases are documented in the description of each method.
func (*ValueError) Error ¶
func (e *ValueError) Error() string
Source Files