github.com/yanyiwu/go@v0.0.0-20150106053140-03d6637dbb7f/test/interface/convert.go (about)

     1  // run
     2  
     3  // Copyright 2009 The Go Authors. All rights reserved.
     4  // Use of this source code is governed by a BSD-style
     5  // license that can be found in the LICENSE file.
     6  
     7  // Test all the different interface conversion runtime functions.
     8  
     9  package main
    10  
    11  type Stringer interface {
    12  	String() string
    13  }
    14  type StringLengther interface {
    15  	String() string
    16  	Length() int
    17  }
    18  type Empty interface{}
    19  
    20  type T string
    21  
    22  func (t T) String() string {
    23  	return string(t)
    24  }
    25  func (t T) Length() int {
    26  	return len(t)
    27  }
    28  
    29  type U string
    30  
    31  func (u U) String() string {
    32  	return string(u)
    33  }
    34  
    35  var t = T("hello")
    36  var u = U("goodbye")
    37  var e Empty
    38  var s Stringer = t
    39  var sl StringLengther = t
    40  var i int
    41  var ok bool
    42  
    43  func hello(s string) {
    44  	if s != "hello" {
    45  		println("not hello: ", s)
    46  		panic("fail")
    47  	}
    48  }
    49  
    50  func five(i int) {
    51  	if i != 5 {
    52  		println("not 5: ", i)
    53  		panic("fail")
    54  	}
    55  }
    56  
    57  func true(ok bool) {
    58  	if !ok {
    59  		panic("not true")
    60  	}
    61  }
    62  
    63  func false(ok bool) {
    64  	if ok {
    65  		panic("not false")
    66  	}
    67  }
    68  
    69  func main() {
    70  	// T2I
    71  	s = t
    72  	hello(s.String())
    73  
    74  	// I2T
    75  	t = s.(T)
    76  	hello(t.String())
    77  
    78  	// T2E
    79  	e = t
    80  
    81  	// E2T
    82  	t = e.(T)
    83  	hello(t.String())
    84  
    85  	// T2I again
    86  	sl = t
    87  	hello(sl.String())
    88  	five(sl.Length())
    89  
    90  	// I2I static
    91  	s = sl
    92  	hello(s.String())
    93  
    94  	// I2I dynamic
    95  	sl = s.(StringLengther)
    96  	hello(sl.String())
    97  	five(sl.Length())
    98  
    99  	// I2E (and E2T)
   100  	e = s
   101  	hello(e.(T).String())
   102  
   103  	// E2I
   104  	s = e.(Stringer)
   105  	hello(s.String())
   106  
   107  	// I2T2 true
   108  	t, ok = s.(T)
   109  	true(ok)
   110  	hello(t.String())
   111  
   112  	// I2T2 false
   113  	_, ok = s.(U)
   114  	false(ok)
   115  
   116  	// I2I2 true
   117  	sl, ok = s.(StringLengther)
   118  	true(ok)
   119  	hello(sl.String())
   120  	five(sl.Length())
   121  
   122  	// I2I2 false (and T2I)
   123  	s = u
   124  	sl, ok = s.(StringLengther)
   125  	false(ok)
   126  
   127  	// E2T2 true
   128  	t, ok = e.(T)
   129  	true(ok)
   130  	hello(t.String())
   131  
   132  	// E2T2 false
   133  	i, ok = e.(int)
   134  	false(ok)
   135  
   136  	// E2I2 true
   137  	sl, ok = e.(StringLengther)
   138  	true(ok)
   139  	hello(sl.String())
   140  	five(sl.Length())
   141  
   142  	// E2I2 false (and T2E)
   143  	e = u
   144  	sl, ok = e.(StringLengther)
   145  	false(ok)
   146  }