| // $G $D/$F.go && $L $F.$A && ./$A.out |
| |
| // Copyright 2009 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. |
| |
| // Check uses of all the different interface |
| // conversion runtime functions. |
| |
| package main |
| |
| type Stringer interface { String() string } |
| type StringLengther interface { String() string; Length() int } |
| type Empty interface { } |
| |
| type T string |
| func (t T) String() string { |
| return string(t); |
| } |
| func (t T) Length() int { |
| return len(t); |
| } |
| |
| type U string |
| func (u U) String() string { |
| return string(u); |
| } |
| |
| var t = T("hello") |
| var u = U("goodbye") |
| var e Empty |
| var s Stringer = t |
| var sl StringLengther = t |
| var i int |
| var ok bool |
| |
| func hello(s string) { |
| if s != "hello" { |
| panic("not hello: ", s); |
| } |
| } |
| |
| func five(i int) { |
| if i != 5 { |
| panic("not 5: ", i); |
| } |
| } |
| |
| func true(ok bool) { |
| if !ok { |
| panic("not true"); |
| } |
| } |
| |
| func false(ok bool) { |
| if ok { |
| panic("not false"); |
| } |
| } |
| |
| func main() { |
| // T2I |
| s = t; |
| hello(s.String()); |
| |
| // I2T |
| t = s.(T); |
| hello(t.String()); |
| |
| // T2E |
| e = t; |
| |
| // E2T |
| t = e.(T); |
| hello(t.String()); |
| |
| // T2I again |
| sl = t; |
| hello(sl.String()); |
| five(sl.Length()); |
| |
| // I2I static |
| s = sl; |
| hello(s.String()); |
| |
| // I2I dynamic |
| sl = s.(StringLengther); |
| hello(sl.String()); |
| five(sl.Length()); |
| |
| // I2E (and E2T) |
| e = s; |
| hello(e.(T).String()); |
| |
| // E2I |
| s = e.(Stringer); |
| hello(s.String()); |
| |
| // I2T2 true |
| t, ok = s.(T); |
| true(ok); |
| hello(t.String()); |
| |
| // I2T2 false |
| var u1 U; |
| u1, ok = s.(U); |
| false(ok); |
| |
| // I2I2 true |
| sl, ok = s.(StringLengther); |
| true(ok); |
| hello(sl.String()); |
| five(sl.Length()); |
| |
| // I2I2 false (and T2I) |
| s = u; |
| sl, ok = s.(StringLengther); |
| false(ok); |
| |
| // E2T2 true |
| t, ok = e.(T); |
| true(ok); |
| hello(t.String()); |
| |
| // E2T2 false |
| i, ok = e.(int); |
| false(ok); |
| |
| // E2I2 true |
| sl, ok = e.(StringLengther); |
| true(ok); |
| hello(sl.String()); |
| five(sl.Length()); |
| |
| // E2I2 false (and T2E) |
| e = u; |
| sl, ok = e.(StringLengther); |
| false(ok); |
| } |
| |