angularjs中的promise
javascript异步回调有好处也有坏处，回调函数大量嵌套十分复杂．所以javascript中还有另一种异步处理模式叫ｐｒｏｍｉｓｅｓ．在angularjs中的实现就是$q服务．
下面是一些小例子．
then,catch,finally
-
在链最后的
catch为整个链式处理提供一个异常处理点 -
在链最后的
finally总是会被执行，不管 promise 被处理或者被拒绝，起清理作用
<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<link rel="stylesheet" href="bootstrap.min.css">
<script src="jquery.min.js"></script>
<script src="angular.min.js"></script>
<script src="bootstrap.min.js"></script>
<script type="text/javascript">
var myapp = angular.module('myapp', []);
myapp.controller('myController', function($scope, $q) {
$scope.send = function() {
var deferred = $q.defer();
var promise = deferred.promise;
promise
.then(function() {
console.log('resolve.....')
}, function() {
console.log('reject.....');
}, function() {
console.log('notify.....');
})
.catch(function() {
console.log('catch..error..')
})
.finally(function() {
console.log('anywhere will be called..');
});
deferred.reject('resolve');
};
});
</script>
<style type="text/css">
</style>
</head>
<body ng-app="myapp">
<div ng-controller="myController">
<button class="btn" ng-click="send()">click</button>
</div>
</body>
</html>
then第三个参数(表征状态)的应用
<!DOCTYPE html>
<html><head>
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<link rel="stylesheet" href="bootstrap.min.css">
<script src="jquery.min.js"></script>
<script src="angular.min.js"></script>
<script src="bootstrap.min.js"></script>
<script type="text/javascript">
var myapp = angular.module('myapp', []);
myapp.controller('myController', function($scope, dataService) {
$scope.send = function() {
dataService.getData()
.then(function success(data) {
console.log(data);
}, function error(error) {
console.log(error);
}, function status(process) {
console.log(process);
});
};
});
myapp.factory('dataService', function($q, $interval) {
return {
getData : function() {
var deferred = $q.defer();
var process = 0;
var interval = $interval(function() {
process += 10;
deferred.notify(process);
//reject之后不再继续运行
// if (process == 50) {
// deferred.reject(process);
// }
if (process >= 100) {
$interval.cancel(interval);
deferred.resolve(process);
}
}, 1000);
return deferred.promise;
}
};
});
</script>
<style type="text/css">
</style>
</head>
<body ng-app="myapp">
<div ng-controller="myController">
<button class="btn" ng-click="send()">click</button>
</div>
</body>
</html>
then链式
<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<link rel="stylesheet" href="bootstrap.min.css">
<script src="jquery.min.js"></script>
<script src="angular.min.js"></script>
<script src="bootstrap.min.js"></script>
<script type="text/javascript">
var myapp = angular.module('myapp', []);
myapp.controller('myController', function($scope, $q) {
$scope.send = function() {
var deferred = $q.defer();
var promise = deferred.promise;
promise
.then(function() {
console.log('1.....')
})
.then(function() {
console.log('2....');
});
deferred.resolve('resolve');
};
});
</script>
<style type="text/css">
</style>
</head>
<body ng-app="myapp">
<div ng-controller="myController">
<button class="btn" ng-click="send()">click</button>
</div>
</body>
</html>
then链会把上一个 then 的返回结果传递给调用链的下一个 then (如果没有就是 undefined).
<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<link rel="stylesheet" href="bootstrap.min.css">
<script src="jquery.min.js"></script>
<script src="angular.min.js"></script>
<script src="bootstrap.min.js"></script>
<script type="text/javascript">
var myapp = angular.module('myapp', []);
myapp.controller('myController', function($scope, $q, $timeout) {
$scope.send = function() {
var deferred = $q.defer();
var promise = deferred.promise;
deferred.resolve('resolve');
promise
.then(function(data) {
console.log(data);
var _deferred = $q.defer();
$timeout(function() {
_deferred.resolve('resolve_');
}, 1000);
return _deferred.promise;
})
.then(function(data) {
console.log(data);
});
};
});
</script>
<style type="text/css">
</style>
</head>
<body ng-app="myapp">
<div ng-controller="myController">
<button class="btn" ng-click="send()">click</button>
</div>
</body>
</html>
如果 then 返回一个 promise 对象，下一个 then 只会在这个 promise 被处理结束的时候调用。