Package reflect
import "reflect"
The reflect package implements run-time reflection, allowing a program to manipulate objects with arbitrary types. The typical use is to take a value with static type interface{} and extract its dynamic type information by calling Typeof, which returns an object with interface type Type. That contains a pointer to a struct of type *StructType, *IntType, etc. representing the details of the underlying type. A type switch or type assertion can reveal which.
A call to NewValue creates a Value representing the run-time data; it contains a *StructValue, *IntValue, etc. MakeZero takes a Type and returns a Value representing a zero value for that type.
Package files
deepequal.go type.go value.gofunc ArrayCopy
func ArrayCopy(dst, src ArrayOrSliceValue) int
ArrayCopy copies the contents of src into dst until either dst has been filled or src has been exhausted. It returns the number of elements copied. The arrays dst and src must have the same element type.
func DeepEqual
func DeepEqual(a1, a2 interface{}) bool
DeepEqual tests for deep equality. It uses normal == equality where possible but will scan members of arrays, slices, and fields of structs. It correctly handles recursive types.
type ArrayOrSliceType
ArrayOrSliceType is the common interface implemented by both ArrayType and SliceType.
type ArrayOrSliceType interface {
Type
Elem() Type
}
type ArrayOrSliceValue
ArrayOrSliceValue is the common interface implemented by both ArrayValue and SliceValue.
type ArrayOrSliceValue interface {
Value
Len() int
Cap() int
Elem(i int) Value
// contains unexported methods
}
type ArrayType
ArrayType represents a fixed array type.
type ArrayType struct {
// contains unexported fields
}
func (*ArrayType) Elem
func (t *ArrayType) Elem() Type
Elem returns the type of the array's elements.
func (*ArrayType) Len
func (t *ArrayType) Len() int
Len returns the number of elements in the array.
type ArrayValue
An ArrayValue represents an array.
type ArrayValue struct {
// contains unexported fields
}
func (*ArrayValue) Cap
func (v *ArrayValue) Cap() int
Cap returns the capacity of the array (equal to Len()).
func (*ArrayValue) Elem
func (v *ArrayValue) Elem(i int) Value
Elem returns the i'th element of v.
func (*ArrayValue) Len
func (v *ArrayValue) Len() int
Len returns the length of the array.
func (*ArrayValue) Set
func (v *ArrayValue) Set(x *ArrayValue)
Set assigns x to v. The new value x must have the same type as v.
func (*ArrayValue) SetValue
func (v *ArrayValue) SetValue(x Value)
Set sets v to the value x.
type BoolType
BoolType represents a boolean type.
type BoolType struct {
// contains unexported fields
}
type BoolValue
BoolValue represents a bool value.
type BoolValue struct {
// contains unexported fields
}
func (*BoolValue) Get
func (v *BoolValue) Get() bool
Get returns the underlying bool value.
func (*BoolValue) Set
func (v *BoolValue) Set(x bool)
Set sets v to the value x.
func (*BoolValue) SetValue
func (v *BoolValue) SetValue(x Value)
Set sets v to the value x.
type ChanDir
ChanDir represents a channel type's direction.
type ChanDir int
const (
RecvDir ChanDir = 1 << iota
SendDir
BothDir = RecvDir | SendDir
)
func (ChanDir) String
func (d ChanDir) String() string
type ChanType
ChanType represents a channel type.
type ChanType struct {
// contains unexported fields
}
func (*ChanType) Dir
func (t *ChanType) Dir() ChanDir
Dir returns the channel direction.
func (*ChanType) Elem
func (t *ChanType) Elem() Type
Elem returns the channel's element type.
type ChanValue
A ChanValue represents a chan.
type ChanValue struct {
// contains unexported fields
}
func MakeChan
func MakeChan(typ *ChanType, buffer int) *ChanValue
MakeChan creates a new channel with the specified type and buffer size.
func (*ChanValue) Cap
func (v *ChanValue) Cap() int
func (*ChanValue) Close
func (v *ChanValue) Close()
Close closes the channel.
func (*ChanValue) Closed
func (v *ChanValue) Closed() bool
Closed returns the result of closed(c) on the underlying channel.
func (*ChanValue) Get
func (v *ChanValue) Get() uintptr
Get returns the uintptr value of v. It is mainly useful for printing.
func (*ChanValue) IsNil
func (v *ChanValue) IsNil() bool
IsNil returns whether v is a nil channel.
func (*ChanValue) Len
func (v *ChanValue) Len() int
func (*ChanValue) Recv
func (v *ChanValue) Recv() Value
Recv receives and returns a value from the channel v.
func (*ChanValue) Send
func (v *ChanValue) Send(x Value)
Send sends x on the channel v.
func (*ChanValue) Set
func (v *ChanValue) Set(x *ChanValue)
Set assigns x to v. The new value x must have the same type as v.
func (*ChanValue) SetValue
func (v *ChanValue) SetValue(x Value)
Set sets v to the value x.
func (*ChanValue) TryRecv
func (v *ChanValue) TryRecv() Value
TryRecv attempts to receive a value from the channel v but will not block. It returns the value if one is received, nil otherwise.
func (*ChanValue) TrySend
func (v *ChanValue) TrySend(x Value) bool
TrySend attempts to sends x on the channel v but will not block. It returns true if the value was sent, false otherwise.
type ComplexType
ComplexType represents a complex type.
type ComplexType struct {
// contains unexported fields
}
type ComplexValue
ComplexValue represents a complex value.
type ComplexValue struct {
// contains unexported fields
}
func (*ComplexValue) Get
func (v *ComplexValue) Get() complex128
Get returns the underlying complex value.
func (*ComplexValue) Set
func (v *ComplexValue) Set(x complex128)
Set sets v to the value x.
func (*ComplexValue) SetValue
func (v *ComplexValue) SetValue(x Value)
Set sets v to the value x.
type FloatType
FloatType represents a float type.
type FloatType struct {
// contains unexported fields
}
type FloatValue
FloatValue represents a float value.
type FloatValue struct {
// contains unexported fields
}
func (*FloatValue) Get
func (v *FloatValue) Get() float64
Get returns the underlying int value.
func (*FloatValue) Overflow
func (v *FloatValue) Overflow(x float64) bool
Overflow returns true if x cannot be represented by the type of v.
func (*FloatValue) Set
func (v *FloatValue) Set(x float64)
Set sets v to the value x.
func (*FloatValue) SetValue
func (v *FloatValue) SetValue(x Value)
Set sets v to the value x.
type FuncType
FuncType represents a function type.
type FuncType struct {
// contains unexported fields
}
func (*FuncType) DotDotDot
func (t *FuncType) DotDotDot() bool
DotDotDot returns true if the final function input parameter is a "..." parameter. If so, t.In(t.NumIn() - 1) returns the parameter's underlying static type []T.
For concreteness, if t is func(x int, y ... float), then
t.NumIn() == 2 t.In(0) is the reflect.Type for "int" t.In(1) is the reflect.Type for "[]float" t.DotDotDot() == true
func (*FuncType) In
func (t *FuncType) In(i int) Type
In returns the type of the i'th function input parameter.
func (*FuncType) NumIn
func (t *FuncType) NumIn() int
NumIn returns the number of input parameters.
func (*FuncType) NumOut
func (t *FuncType) NumOut() int
NumOut returns the number of function output parameters.
func (*FuncType) Out
func (t *FuncType) Out(i int) Type
Out returns the type of the i'th function output parameter.
type FuncValue
A FuncValue represents a function value.
type FuncValue struct {
// contains unexported fields
}
func (*FuncValue) Call
func (fv *FuncValue) Call(in []Value) []Value
Call calls the function fv with input parameters in. It returns the function's output parameters as Values.
func (*FuncValue) Get
func (v *FuncValue) Get() uintptr
Get returns the uintptr value of v. It is mainly useful for printing.
func (*FuncValue) IsNil
func (v *FuncValue) IsNil() bool
IsNil returns whether v is a nil function.
func (*FuncValue) Set
func (v *FuncValue) Set(x *FuncValue)
Set assigns x to v. The new value x must have the same type as v.
func (*FuncValue) SetValue
func (v *FuncValue) SetValue(x Value)
Set sets v to the value x.
type IntType
IntType represents a signed integer type.
type IntType struct {
// contains unexported fields
}
type IntValue
IntValue represents an int value.
type IntValue struct {
// contains unexported fields
}
func (*IntValue) Get
func (v *IntValue) Get() int64
Get returns the underlying int value.
func (*IntValue) Overflow
func (v *IntValue) Overflow(x int64) bool
Overflow returns true if x cannot be represented by the type of v.
func (*IntValue) Set
func (v *IntValue) Set(x int64)
Set sets v to the value x.
func (*IntValue) SetValue
func (v *IntValue) SetValue(x Value)
Set sets v to the value x.
type InterfaceType
InterfaceType represents an interface type.
type InterfaceType struct {
// contains unexported fields
}
func (*InterfaceType) Method
func (t *InterfaceType) Method(i int) (m Method)
Method returns the i'th interface method.
func (*InterfaceType) NumMethod
func (t *InterfaceType) NumMethod() int
NumMethod returns the number of interface methods.
type InterfaceValue
An InterfaceValue represents an interface value.
type InterfaceValue struct {
// contains unexported fields
}
func (*InterfaceValue) Elem
func (v *InterfaceValue) Elem() Value
Elem returns the concrete value stored in the interface value v.
func (*InterfaceValue) IsNil
func (v *InterfaceValue) IsNil() bool
IsNil returns whether v is a nil interface value.
func (*InterfaceValue) Method
func (v *InterfaceValue) Method(i int) *FuncValue
Method returns a FuncValue corresponding to v's i'th method. The arguments to a Call on the returned FuncValue should not include a receiver; the FuncValue will use v as the receiver.
func (*InterfaceValue) Set
func (v *InterfaceValue) Set(x Value)
Set assigns x to v.
func (*InterfaceValue) SetValue
func (v *InterfaceValue) SetValue(x Value)
Set sets v to the value x.
type Kind
A Kind represents the specific kind of type that a Type represents. For numeric types, the Kind gives more information than the Type's dynamic type. For example, the Type of a float32 is FloatType, but the Kind is Float32.
The zero Kind is not a valid kind.
type Kind uint8
const (
Bool Kind = 1 + iota
Int
Int8
Int16
Int32
Int64
Uint
Uint8
Uint16
Uint32
Uint64
Uintptr
Float
Float32
Float64
Complex
Complex64
Complex128
Array
Chan
Func
Interface
Map
Ptr
Slice
String
Struct
UnsafePointer
)
func (Kind) String
func (k Kind) String() string
type MapType
MapType represents a map type.
type MapType struct {
// contains unexported fields
}
func (*MapType) Elem
func (t *MapType) Elem() Type
Elem returns the map element type.
func (*MapType) Key
func (t *MapType) Key() Type
Key returns the map key type.
type MapValue
A MapValue represents a map value.
type MapValue struct {
// contains unexported fields
}
func MakeMap
func MakeMap(typ *MapType) *MapValue
MakeMap creates a new map of the specified type.
func (*MapValue) Elem
func (v *MapValue) Elem(key Value) Value
Elem returns the value associated with key in the map v. It returns nil if key is not found in the map.
func (*MapValue) Get
func (v *MapValue) Get() uintptr
Get returns the uintptr value of v. It is mainly useful for printing.
func (*MapValue) IsNil
func (v *MapValue) IsNil() bool
IsNil returns whether v is a nil map value.
func (*MapValue) Keys
func (v *MapValue) Keys() []Value
Keys returns a slice containing all the keys present in the map, in unspecified order.
func (*MapValue) Len
func (v *MapValue) Len() int
Len returns the number of keys in the map v.
func (*MapValue) Set
func (v *MapValue) Set(x *MapValue)
Set assigns x to v. The new value x must have the same type as v.
func (*MapValue) SetElem
func (v *MapValue) SetElem(key, val Value)
SetElem sets the value associated with key in the map v to val. If val is nil, Put deletes the key from map.
func (*MapValue) SetValue
func (v *MapValue) SetValue(x Value)
Set sets v to the value x.
type Method
Method represents a single method.
type Method struct {
PkgPath string // empty for uppercase Name
Name string
Type *FuncType
Func *FuncValue
}
type PtrType
PtrType represents a pointer type.
type PtrType struct {
// contains unexported fields
}
func (*PtrType) Elem
func (t *PtrType) Elem() Type
Elem returns the pointer element type.
type PtrValue
A PtrValue represents a pointer.
type PtrValue struct {
// contains unexported fields
}
func (*PtrValue) Elem
func (v *PtrValue) Elem() Value
Elem returns the value that v points to. If v is a nil pointer, Elem returns a nil Value.
func (*PtrValue) Get
func (v *PtrValue) Get() uintptr
Get returns the uintptr value of v. It is mainly useful for printing.
func (*PtrValue) IsNil
func (v *PtrValue) IsNil() bool
IsNil returns whether v is a nil pointer.
func (*PtrValue) PointTo
func (v *PtrValue) PointTo(x Value)
PointTo changes v to point to x. If x is a nil Value, PointTo sets v to nil.
func (*PtrValue) Set
func (v *PtrValue) Set(x *PtrValue)
Set assigns x to v. The new value x must have the same type as v.
func (*PtrValue) SetValue
func (v *PtrValue) SetValue(x Value)
Set sets v to the value x.
type SliceHeader
runtime representation of slice
type SliceHeader struct {
Data uintptr
Len int
Cap int
}
type SliceType
SliceType represents a slice type.
type SliceType struct {
// contains unexported fields
}
func (*SliceType) Elem
func (t *SliceType) Elem() Type
Elem returns the type of the slice's elements.
type SliceValue
A SliceValue represents a slice.
type SliceValue struct {
// contains unexported fields
}
func MakeSlice
func MakeSlice(typ *SliceType, len, cap int) *SliceValue
MakeSlice creates a new zero-initialized slice value for the specified slice type, length, and capacity.
func (*SliceValue) Cap
func (v *SliceValue) Cap() int
Cap returns the capacity of the slice.
func (*SliceValue) Elem
func (v *SliceValue) Elem(i int) Value
Elem returns the i'th element of v.
func (*SliceValue) Get
func (v *SliceValue) Get() uintptr
Get returns the uintptr address of the v.Cap()'th element. This gives the same result for all slices of the same array. It is mainly useful for printing.
func (*SliceValue) IsNil
func (v *SliceValue) IsNil() bool
IsNil returns whether v is a nil slice.
func (*SliceValue) Len
func (v *SliceValue) Len() int
Len returns the length of the slice.
func (*SliceValue) Set
func (v *SliceValue) Set(x *SliceValue)
Set assigns x to v. The new value x must have the same type as v.
func (*SliceValue) SetLen
func (v *SliceValue) SetLen(n int)
SetLen changes the length of v. The new length n must be between 0 and the capacity, inclusive.
func (*SliceValue) SetValue
func (v *SliceValue) SetValue(x Value)
Set sets v to the value x.
func (*SliceValue) Slice
func (v *SliceValue) Slice(beg, end int) *SliceValue
Slice returns a sub-slice of the slice v.
type StringHeader
StringHeader is the runtime representation of a string.
type StringHeader struct {
Data uintptr
Len int
}
type StringType
StringType represents a string type.
type StringType struct {
// contains unexported fields
}
type StringValue
StringValue represents a string value.
type StringValue struct {
// contains unexported fields
}
func (*StringValue) Get
func (v *StringValue) Get() string
Get returns the underlying string value.
func (*StringValue) Set
func (v *StringValue) Set(x string)
Set sets v to the value x.
func (*StringValue) SetValue
func (v *StringValue) SetValue(x Value)
Set sets v to the value x.
type StructField
type StructField struct {
PkgPath string // empty for uppercase Name
Name string
Type Type
Tag string
Offset uintptr
Index []int
Anonymous bool
}
type StructType
StructType represents a struct type.
type StructType struct {
// contains unexported fields
}
func (*StructType) Field
func (t *StructType) Field(i int) (f StructField)
Field returns the i'th struct field.
func (*StructType) FieldByIndex
func (t *StructType) FieldByIndex(index []int) (f StructField)
FieldByIndex returns the nested field corresponding to index.
func (*StructType) FieldByName
func (t *StructType) FieldByName(name string) (f StructField, present bool)
FieldByName returns the struct field with the given name and a boolean to indicate if the field was found.
func (*StructType) FieldByNameFunc
func (t *StructType) FieldByNameFunc(match func(string) bool) (f StructField, present bool)
FieldByNameFunc returns the struct field with a name that satisfies the match function and a boolean to indicate if the field was found.
func (*StructType) NumField
func (t *StructType) NumField() int
NumField returns the number of struct fields.
type StructValue
A StructValue represents a struct value.
type StructValue struct {
// contains unexported fields
}
func (*StructValue) Field
func (v *StructValue) Field(i int) Value
Field returns the i'th field of the struct.
func (*StructValue) FieldByIndex
func (t *StructValue) FieldByIndex(index []int) (v Value)
FieldByIndex returns the nested field corresponding to index.
func (*StructValue) FieldByName
func (t *StructValue) FieldByName(name string) Value
FieldByName returns the struct field with the given name. The result is nil if no field was found.
func (*StructValue) FieldByNameFunc
func (t *StructValue) FieldByNameFunc(match func(string) bool) Value
FieldByNameFunc returns the struct field with a name that satisfies the match function. The result is nil if no field was found.
func (*StructValue) NumField
func (v *StructValue) NumField() int
NumField returns the number of fields in the struct.
func (*StructValue) Set
func (v *StructValue) Set(x *StructValue)
Set assigns x to v. The new value x must have the same type as v.
func (*StructValue) SetValue
func (v *StructValue) SetValue(x Value)
Set sets v to the value x.
type Type
Type is the runtime representation of a Go type. Every type implements the methods listed here. Some types implement additional interfaces; use a type switch to find out what kind of type a Type is. Each type in a program has a unique Type, so == on Types corresponds to Go's type equality.
type Type interface {
// PkgPath returns the type's package path.
// The package path is a full package import path like "container/vector".
// PkgPath returns an empty string for unnamed types.
PkgPath() string
// Name returns the type's name within its package.
// Name returns an empty string for unnamed types.
Name() string
// String returns a string representation of the type.
// The string representation may use shortened package names
// (e.g., vector instead of "container/vector") and is not
// guaranteed to be unique among types. To test for equality,
// compare the Types directly.
String() string
// Size returns the number of bytes needed to store
// a value of the given type; it is analogous to unsafe.Sizeof.
Size() uintptr
// Bits returns the size of the type in bits.
// It is intended for use with numeric types and may overflow
// when used for composite types.
Bits() int
// Align returns the alignment of a value of this type
// when allocated in memory.
Align() int
// FieldAlign returns the alignment of a value of this type
// when used as a field in a struct.
FieldAlign() int
// Kind returns the specific kind of this type.
Kind() Kind
// For non-interface types, Method returns the i'th method with receiver T.
// For interface types, Method returns the i'th method in the interface.
// NumMethod returns the number of such methods.
Method(int) Method
NumMethod() int
// contains unexported methods
}
func Typeof
func Typeof(i interface{}) Type
Typeof returns the reflection Type of the value in the interface{}.
type UintType
UintType represents a uint type.
type UintType struct {
// contains unexported fields
}
type UintValue
UintValue represents a uint value.
type UintValue struct {
// contains unexported fields
}
func (*UintValue) Get
func (v *UintValue) Get() uint64
Get returns the underlying uuint value.
func (*UintValue) Overflow
func (v *UintValue) Overflow(x uint64) bool
Overflow returns true if x cannot be represented by the type of v.
func (*UintValue) Set
func (v *UintValue) Set(x uint64)
Set sets v to the value x.
func (*UintValue) SetValue
func (v *UintValue) SetValue(x Value)
Set sets v to the value x.
type UnsafePointerType
UnsafePointerType represents an unsafe.Pointer type.
type UnsafePointerType struct {
// contains unexported fields
}
type UnsafePointerValue
UnsafePointerValue represents an unsafe.Pointer value.
type UnsafePointerValue struct {
// contains unexported fields
}
func (*UnsafePointerValue) Get
func (v *UnsafePointerValue) Get() uintptr
Get returns the underlying uintptr value. Get returns uintptr, not unsafe.Pointer, so that programs that do not import "unsafe" cannot obtain a value of unsafe.Pointer type from "reflect".
func (*UnsafePointerValue) Set
func (v *UnsafePointerValue) Set(x unsafe.Pointer)
Set sets v to the value x.
func (*UnsafePointerValue) SetValue
func (v *UnsafePointerValue) SetValue(x Value)
Set sets v to the value x.
type Value
Value is the common interface to reflection values. The implementations of Value (e.g., ArrayValue, StructValue) have additional type-specific methods.
type Value interface {
// Type returns the value's type.
Type() Type
// Interface returns the value as an interface{}.
Interface() interface{}
// CanSet returns whether the value can be changed.
// Values obtained by the use of non-exported struct fields
// can be used in Get but not Set.
// If CanSet() returns false, calling the type-specific Set
// will cause a crash.
CanSet() bool
// SetValue assigns v to the value; v must have the same type as the value.
SetValue(v Value)
// Addr returns a pointer to the underlying data.
// It is for advanced clients that also
// import the "unsafe" package.
Addr() uintptr
// Method returns a FuncValue corresponding to the value's i'th method.
// The arguments to a Call on the returned FuncValue
// should not include a receiver; the FuncValue will use
// the value as the receiver.
Method(i int) *FuncValue
// contains unexported methods
}
func Indirect
func Indirect(v Value) Value
Indirect returns the value that v points to. If v is a nil pointer, Indirect returns a nil Value. If v is not a pointer, Indirect returns v.
func MakeZero
func MakeZero(typ Type) Value
MakeZero returns a zero Value for the specified Type.
func NewValue
func NewValue(i interface{}) Value
NewValue returns a new Value initialized to the concrete value stored in the interface i. NewValue(nil) returns nil.