Documentation
¶
Index ¶
- Constants
- type ChanDir
- type Kind
- type Method
- type StructField
- type StructTag
- type Type
- type Value
- func (v Value) Addr() Value
- func (v Value) Bool() bool
- func (v Value) Bytes() []byte
- func (v Value) CanFloat() bool
- func (v Value) CanInt() bool
- func (v Value) CanInterface() bool
- func (v Value) Float() float64
- func (v Value) Grow(n int)
- func (v Value) Index(i int) Value
- func (v Value) Int() int64
- func (v Value) Interface() (i any)
- func (v Value) InterfaceData() [2]uintptrdeprecated
- func (v Value) IsNil() bool
- func (v Value) IsValid() bool
- func (v Value) IsZero() bool
- func (v Value) Kind() Kind
- func (v Value) Len() int
- func (v Value) Set(x Value)
- func (v Value) SetBool(x bool)
- func (v Value) SetBytes(x []byte)
- func (v Value) SetComplex(x complex128)
- func (v Value) SetFloat(x float64)
- func (v Value) SetInt(x int64)
- func (v Value) SetZero()
- 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 Method ¶
type Method struct {
// Name is the method name.
Name string
// PkgPath is the package path that qualifies a lower case (unexported)
// method name. It is empty for upper case (exported) method names.
// The combination of PkgPath and Name uniquely identifies a method
// in a method set.
// See https://golang.org/ref/spec#Uniqueness_of_identifiers
PkgPath string
Type Type // method type
Func Value // func with receiver as first argument
Index int // index for Type.Method
}
Method represents a single method.
func (Method) IsExported ¶
IsExported reports whether the method is exported.
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.
func (StructField) IsExported ¶
func (f StructField) IsExported() bool
IsExported reports whether the field is exported.
type StructTag ¶
type StructTag string
A StructTag is the tag string in a struct field.
By convention, tag strings are a concatenation of optionally space-separated key:"value" pairs. Each key is a non-empty string consisting of non-control characters other than space (U+0020 ' '), quote (U+0022 '"'), and colon (U+003A ':'). Each value is quoted using U+0022 '"' characters and Go string literal syntax.
func (StructTag) Get ¶
Get returns the value associated with key in the tag string. If there is no such key in the tag, Get returns the empty string. If the tag does not have the conventional format, the value returned by Get is unspecified. To determine whether a tag is explicitly set to the empty string, use Lookup.
func (StructTag) Lookup ¶
Lookup returns the value associated with key in the tag string. If the key is present in the tag the value (which may be empty) is returned. Otherwise the returned value will be the empty string. The ok return value reports whether the value was explicitly set in the tag string. If the tag does not have the conventional format, the value returned by Lookup is unspecified.
type Type ¶
type Type interface {
// Align returns the alignment in bytes of a value of
// this type when allocated in memory.
Align() int
// FieldAlign returns the alignment in bytes of a value of
// this type when used as a field in a struct.
FieldAlign() int
// Method returns the i'th method in the type's method set.
// It panics if i is not in the range [0, NumMethod()).
//
// For a non-interface type T or *T, the returned Method's Type and Func
// fields describe a function whose first argument is the receiver,
// and only exported methods are accessible.
//
// For an interface type, the returned Method's Type field gives the
// method signature, without a receiver, and the Func field is nil.
//
// Methods are sorted in lexicographic order.
Method(int) Method
// MethodByName returns the method with that name in the type's
// method set and a boolean indicating if the method was found.
//
// For a non-interface type T or *T, the returned Method's Type and Func
// fields describe a function whose first argument is the receiver.
//
// For an interface type, the returned Method's Type field gives the
// method signature, without a receiver, and the Func field is nil.
MethodByName(string) (Method, bool)
// 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
// Size returns the number of bytes needed to store
// a value of the given type; it is analogous to unsafe.Sizeof.
Size() uintptr
// 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
// Implements reports whether the type implements the interface type u.
Implements(u Type) bool
// AssignableTo reports whether a value of the type is assignable to type u.
AssignableTo(u Type) bool
// 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
// Comparable reports whether values of this type are comparable.
// Even if Comparable returns true, the comparison may still panic.
// For example, values of interface type are comparable,
// but the comparison will panic if their dynamic type is not comparable.
Comparable() bool
// Bits returns the size of the type in bits.
// It panics if the type's Kind is not one of the
// sized or unsized Int, Uint, Float, or Complex kinds.
Bits() int
// 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
// FieldByIndex returns the nested field corresponding
// to the index sequence. It is equivalent to calling Field
// successively for each index i.
// It panics if the type's Kind is not Struct.
FieldByIndex(index []int) StructField
// FieldByName returns the struct field with the given name
// and a boolean indicating if the field was found.
FieldByName(name string) (StructField, bool)
// FieldByNameFunc returns the struct field with a name
// that satisfies the match function and a boolean indicating if
// the field was found.
//
// FieldByNameFunc considers the fields in the struct itself
// and then the fields in any embedded structs, in breadth first order,
// stopping at the shallowest nesting depth containing one or more
// fields satisfying the match function. If multiple fields at that depth
// satisfy the match function, they cancel each other
// and FieldByNameFunc returns no match.
// This behavior mirrors Go's handling of name lookup in
// structs containing embedded fields.
FieldByNameFunc(match func(string) bool) (StructField, bool)
// 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.
func PointerTo ¶
PointerTo returns the pointer type with element t. For example, if t represents type Foo, PointerTo(t) represents *Foo.
func PtrTo ¶
PtrTo returns the pointer type with element t. For example, if t represents type Foo, PtrTo(t) represents *Foo.
PtrTo is the old spelling of PointerTo. The two functions behave identically.
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 Append ¶
Append appends the values x to a slice s and returns the resulting slice. As in Go, each x's value must be assignable to the slice's element type.
func AppendSlice ¶
AppendSlice appends a slice t to a slice s and returns the resulting slice. The slices s and t must have the same element type.
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 ¶
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) Addr ¶
Addr returns a pointer value representing the address of v. It panics if CanAddr() returns false. Addr is typically used to obtain a pointer to a struct field or slice element in order to call a method that requires a pointer receiver.
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) CanInterface ¶
CanInterface reports whether Interface can be used without panicking.
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) Grow ¶
Grow increases the slice's capacity, if necessary, to guarantee space for another n elements. After Grow(n), at least n elements can be appended to the slice without another allocation.
It panics if v's Kind is not a Slice or if n is negative or too large to allocate the memory.
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 ¶
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) InterfaceData
deprecated
InterfaceData returns a pair of unspecified uintptr values. It panics if v's Kind is not Interface.
In earlier versions of Go, this function returned the interface's value as a uintptr pair. As of Go 1.4, the implementation of interface values precludes any defined use of InterfaceData.
Deprecated: The memory representation of interface values is not compatible with InterfaceData.
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) IsZero ¶
IsZero reports whether v is the zero value for its type. It panics if the argument is invalid.
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) 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 and must not be derived from an unexported field.
func (Value) SetBool ¶
SetBool sets v's underlying value. It panics if v's Kind is not Bool or if CanSet() is false.
func (Value) SetBytes ¶
SetBytes sets v's underlying value. It panics if v's underlying value is not a slice of bytes.
func (Value) SetComplex ¶
func (v Value) SetComplex(x complex128)
SetComplex sets v's underlying value to x. It panics if v's Kind is not Complex64 or Complex128, or if CanSet() is false.
func (Value) SetFloat ¶
SetFloat sets v's underlying value to x. It panics if v's Kind is not Float32 or Float64, or if CanSet() is false.
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