我希望通过Firebase事务增加几个计数器,并在firebase中添加一个新值.关键是我要确保它是否全部成功保存任何数据.
我想这最好用承诺来完成吗？不幸的是我对它们不是很熟悉
到目前为止,我有：
$scope.addNewPost = function() {
var ref = new Firebase(FBURL).child('/posts').push();
var onComplete = function(error) {
if (error) {
alert('Error: Something went wrong when creating your post please try again');
throw new Error(error);
} else {
$scope.reset(); // or redirect to post
}
};
var tags = $scope.post.tags.split(',');
console.log(tags);
angular.forEach(tags,function(value,index){
var refTag = new Firebase(FBURL).child('/tags/' + value);
refTag.transaction(function(current_value) {
return current_value + 1;
});
});
ref.set($scope.post,onComplete);
};
任何人都可以指点我如何实现这一点或提供建议吗？
也许有更好的Angularfire方法来做到这一点？
将跟进问题移至new question dealing specifically with error handling
解决方法
您可能希望将
$q.all视为承诺的包装器.基本上,如果所有承诺都成功完成承诺列表,则会解决$q.all承诺,否则将被拒绝.
//assuming $q is injected as a service
var transactions = [];
angular.forEach(tags,index){
var dfd = $q.defer();
var refTag = new Firebase(FBURL).child('/tags/' + value);
refTag.transaction(function(current_value) {
dfd.resolve( current_value + 1 );
return current_value + 1;
});
transactions.push( dfd.promise );
});
$q.all( transactions ).then(
function(){
/*Resolved values of the promises are set to arguments in order*/
ref.set( $scope.post,onComplete );
},function(){
//generally handle errors here,but your example does not show rejections are possible
}
)
