diff options
| -rw-r--r-- | dart.html.markdown | 44 |
1 files changed, 34 insertions, 10 deletions
diff --git a/dart.html.markdown b/dart.html.markdown index 76857306..e12a4ed5 100644 --- a/dart.html.markdown +++ b/dart.html.markdown @@ -176,23 +176,47 @@ example13() { match(s2); } -// Boolean expressions need to resolve to either true or false, as no -// implicit conversions are supported. +// Boolean expressions support implicit conversions and dynamic type example14() { - var v = true; - if (v) { - print("Example14 value is true"); + var a = true; + if (a) { + print("true, a is $a"); } - v = null; + a = null; + if (a) { + print("true, a is $a"); + } else { + print("false, a is $a"); // runs here + } + + // dynamic typed null can be convert to bool + var b;// b is dynamic type + b = "abc"; try { - if (v) { - // Never runs + if (b) { + print("true, b is $b"); } else { - // Never runs + print("false, b is $b"); } } catch (e) { - print("Example14 null value causes an exception: '${e}'"); + print("error, b is $b"); // this could be run but got error } + b = null; + if (b) { + print("true, b is $b"); + } else { + print("false, b is $b"); // runs here + } + + // statically typed null can not be convert to bool + var c = "abc"; + c = null; + // complie failed + // if (c) { + // print("true, c is $c"); + // } else { + // print("false, c is $c"); + // } } // try/catch/finally and throw are used for exception handling. |