golang new与make的一点区别理解

方法注释可以看出
1、new可以实力化任何类型，返回一个类型的指针，指针指向该类型的零值
slice:= new([]int)
可以直接使用slice01 := append(*slice,1,2,3)
map := new(map[int]string) 貌似不可以直接使用 map 指针指向nil *map == nil 为true
2、make 值可以实力化slice,map,channal三种类型，返回这三种类新的实例化对象本身，可以直接使用

具体区别可以看源码注释
通过new的 slice 之所以能用，应该是append引起的底层数组重新分配了，因为append会判断cap的容量，如果容量不够会重新分配底层数组，cap方法即使slice为nil，cap的值为零

// Copyright 2011 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file./*Package builtin provides documentation for Go's predeclared identifiers.The items documented here are not actually in package builtinbut their descriptions here allow godoc to present documentationfor the language's special identifiers.
*/
package builtin// bool is the set of boolean values, true and false.
type bool bool// true and false are the two untyped boolean values.
const (true  = 0 == 0 // Untyped bool.false = 0 != 0 // Untyped bool.
)// uint8 is the set of all unsigned 8-bit integers.
// Range: 0 through 255.
type uint8 uint8// uint16 is the set of all unsigned 16-bit integers.
// Range: 0 through 65535.
type uint16 uint16// uint32 is the set of all unsigned 32-bit integers.
// Range: 0 through 4294967295.
type uint32 uint32// uint64 is the set of all unsigned 64-bit integers.
// Range: 0 through 18446744073709551615.
type uint64 uint64// int8 is the set of all signed 8-bit integers.
// Range: -128 through 127.
type int8 int8// int16 is the set of all signed 16-bit integers.
// Range: -32768 through 32767.
type int16 int16// int32 is the set of all signed 32-bit integers.
// Range: -2147483648 through 2147483647.
type int32 int32// int64 is the set of all signed 64-bit integers.
// Range: -9223372036854775808 through 9223372036854775807.
type int64 int64// float32 is the set of all IEEE-754 32-bit floating-point numbers.
type float32 float32// float64 is the set of all IEEE-754 64-bit floating-point numbers.
type float64 float64// complex64 is the set of all complex numbers with float32 real and
// imaginary parts.
type complex64 complex64// complex128 is the set of all complex numbers with float64 real and
// imaginary parts.
type complex128 complex128// string is the set of all strings of 8-bit bytes, conventionally but not
// necessarily representing UTF-8-encoded text. A string may be empty, but
// not nil. Values of string type are immutable.
type string string// int is a signed integer type that is at least 32 bits in size. It is a
// distinct type, however, and not an alias for, say, int32.
type int int// uint is an unsigned integer type that is at least 32 bits in size. It is a
// distinct type, however, and not an alias for, say, uint32.
type uint uint// uintptr is an integer type that is large enough to hold the bit pattern of
// any pointer.
type uintptr uintptr// byte is an alias for uint8 and is equivalent to uint8 in all ways. It is
// used, by convention, to distinguish byte values from 8-bit unsigned
// integer values.
type byte = uint8// rune is an alias for int32 and is equivalent to int32 in all ways. It is
// used, by convention, to distinguish character values from integer values.
type rune = int32// iota is a predeclared identifier representing the untyped integer ordinal
// number of the current const specification in a (usually parenthesized)
// const declaration. It is zero-indexed.
const iota = 0 // Untyped int.// nil is a predeclared identifier representing the zero value for a
// pointer, channel, func, interface, map, or slice type.
var nil Type // Type must be a pointer, channel, func, interface, map, or slice type// Type is here for the purposes of documentation only. It is a stand-in
// for any Go type, but represents the same type for any given function
// invocation.
type Type int// Type1 is here for the purposes of documentation only. It is a stand-in
// for any Go type, but represents the same type for any given function
// invocation.
type Type1 int// IntegerType is here for the purposes of documentation only. It is a stand-in
// for any integer type: int, uint, int8 etc.
type IntegerType int// FloatType is here for the purposes of documentation only. It is a stand-in
// for either float type: float32 or float64.
type FloatType float32// ComplexType is here for the purposes of documentation only. It is a
// stand-in for either complex type: complex64 or complex128.
type ComplexType complex64// The append built-in function appends elements to the end of a slice. If
// it has sufficient capacity, the destination is resliced to accommodate the
// new elements. If it does not, a new underlying array will be allocated.
// Append returns the updated slice. It is therefore necessary to store the
// result of append, often in the variable holding the slice itself:
//  slice = append(slice, elem1, elem2)
//  slice = append(slice, anotherSlice...)
// As a special case, it is legal to append a string to a byte slice, like this:
//  slice = append([]byte("hello "), "world"...)
func append(slice []Type, elems ...Type) []Type// The copy built-in function copies elements from a source slice into a
// destination slice. (As a special case, it also will copy bytes from a
// string to a slice of bytes.) The source and destination may overlap. Copy
// returns the number of elements copied, which will be the minimum of
// len(src) and len(dst).
func copy(dst, src []Type) int// The delete built-in function deletes the element with the specified key
// (m[key]) from the map. If m is nil or there is no such element, delete
// is a no-op.
func delete(m map[Type]Type1, key Type)// The len built-in function returns the length of v, according to its type:
//  Array: the number of elements in v.
//  Pointer to array: the number of elements in *v (even if v is nil).
//  Slice, or map: the number of elements in v; if v is nil, len(v) is zero.
//  String: the number of bytes in v.
//  Channel: the number of elements queued (unread) in the channel buffer;
//           if v is nil, len(v) is zero.
// For some arguments, such as a string literal or a simple array expression, the
// result can be a constant. See the Go language specification's "Length and
// capacity" section for details.
func len(v Type) int// The cap built-in function returns the capacity of v, according to its type:
//  Array: the number of elements in v (same as len(v)).
//  Pointer to array: the number of elements in *v (same as len(v)).
//  Slice: the maximum length the slice can reach when resliced;
//  if v is nil, cap(v) is zero.
//  Channel: the channel buffer capacity, in units of elements;
//  if v is nil, cap(v) is zero.
// For some arguments, such as a simple array expression, the result can be a
// constant. See the Go language specification's "Length and capacity" section for
// details.
func cap(v Type) int// The make built-in function allocates and initializes an object of type
// slice, map, or chan (only). Like new, the first argument is a type, not a
// value. Unlike new, make's return type is the same as the type of its
// argument, not a pointer to it. The specification of the result depends on
// the type:
//  Slice: The size specifies the length. The capacity of the slice is
//  equal to its length. A second integer argument may be provided to
//  specify a different capacity; it must be no smaller than the
//  length. For example, make([]int, 0, 10) allocates an underlying array
//  of size 10 and returns a slice of length 0 and capacity 10 that is
//  backed by this underlying array.
//  Map: An empty map is allocated with enough space to hold the
//  specified number of elements. The size may be omitted, in which case
//  a small starting size is allocated.
//  Channel: The channel's buffer is initialized with the specified
//  buffer capacity. If zero, or the size is omitted, the channel is
//  unbuffered.
func make(t Type, size ...IntegerType) Type// The new built-in function allocates memory. The first argument is a type,
// not a value, and the value returned is a pointer to a newly
// allocated zero value of that type.
func new(Type) *Type// The complex built-in function constructs a complex value from two
// floating-point values. The real and imaginary parts must be of the same
// size, either float32 or float64 (or assignable to them), and the return
// value will be the corresponding complex type (complex64 for float32,
// complex128 for float64).
func complex(r, i FloatType) ComplexType// The real built-in function returns the real part of the complex number c.
// The return value will be floating point type corresponding to the type of c.
func real(c ComplexType) FloatType// The imag built-in function returns the imaginary part of the complex
// number c. The return value will be floating point type corresponding to
// the type of c.
func imag(c ComplexType) FloatType// The close built-in function closes a channel, which must be either
// bidirectional or send-only. It should be executed only by the sender,
// never the receiver, and has the effect of shutting down the channel after
// the last sent value is received. After the last value has been received
// from a closed channel c, any receive from c will succeed without
// blocking, returning the zero value for the channel element. The form
//  x, ok := <-c
// will also set ok to false for a closed channel.
func close(c chan<- Type)// The panic built-in function stops normal execution of the current
// goroutine. When a function F calls panic, normal execution of F stops
// immediately. Any functions whose execution was deferred by F are run in
// the usual way, and then F returns to its caller. To the caller G, the
// invocation of F then behaves like a call to panic, terminating G's
// execution and running any deferred functions. This continues until all
// functions in the executing goroutine have stopped, in reverse order. At
// that point, the program is terminated with a non-zero exit code. This
// termination sequence is called panicking and can be controlled by the
// built-in function recover.
func panic(v interface{})// The recover built-in function allows a program to manage behavior of a
// panicking goroutine. Executing a call to recover inside a deferred
// function (but not any function called by it) stops the panicking sequence
// by restoring normal execution and retrieves the error value passed to the
// call of panic. If recover is called outside the deferred function it will
// not stop a panicking sequence. In this case, or when the goroutine is not
// panicking, or if the argument supplied to panic was nil, recover returns
// nil. Thus the return value from recover reports whether the goroutine is
// panicking.
func recover() interface{}// The print built-in function formats its arguments in an
// implementation-specific way and writes the result to standard error.
// Print is useful for bootstrapping and debugging; it is not guaranteed
// to stay in the language.
func print(args ...Type)// The println built-in function formats its arguments in an
// implementation-specific way and writes the result to standard error.
// Spaces are always added between arguments and a newline is appended.
// Println is useful for bootstrapping and debugging; it is not guaranteed
// to stay in the language.
func println(args ...Type)// The error built-in interface type is the conventional interface for
// representing an error condition, with the nil value representing no error.
type error interface {Error() string
}

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golang new与make的一点区别理解

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