如何在dart中执行此jquery模式? [英] How do I do this jquery pattern in dart?
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问题描述
我试图将以下javascript / jquery代码转换为dart,但我无法理解期货如何工作。
function fnA(){
fnB()。then(function(){
// do something
}
}
function fnB(){
var ret = $ .Deferred();
_db.open(database_name).then(function(){
var defers = [];
_db.keys()。forEach(function(key_name){
var key_dfd = $ .Deferred();
defers.push(key_dfd);
_db.getByKey(key_name).then(function(data){
key_dfd.resolve(data);
});
});
$ .when defers).then(ret.resolve);
})
.fail(function(){
ret.reject();
});
return ret.promise();
}
到以下,但它似乎不工作:
(我正在为数据库使用lawndart)
< pre(=){
//这里,所有的键应该已经被删除了。 loaded
});
}
未来的fnB(){
return _db.open()。((_){
return _db.keys()。forEach key_name){
return _db.getByKey(key_name).then((String data){
// do something with data
return data;
});
});
});
}
解决方案
't test the code:
void fnA
fnB()。then((_){
//这里,所有的键应该已经加载了
});
}
未来的fnB(){
return _db.open()。then((_){
List< Future> futures = [];
return _db.keys()。forEach((String key_name){
futures.add(_db.getByKey(key_name).then((String data){
// do something with data
return data;
}));
}); then(()=> Future.wait(futures));
});
}
I'm trying to convert the following javascript/jquery code into dart, but I'm having problems understanding how futures work.
function fnA() {
fnB().then(function() {
// do something
}
}
function fnB() {
var ret = $.Deferred();
_db.open(database_name).then(function() {
var defers = [];
_db.keys().forEach(function(key_name) {
var key_dfd = $.Deferred();
defers.push(key_dfd);
_db.getByKey(key_name).then(function(data) {
key_dfd.resolve(data);
});
});
$.when(defers).then(ret.resolve);
})
.fail(function() {
ret.reject();
});
return ret.promise();
}
I thought I could do it similar to following, but it doesn't seem to work:
(I'm using lawndart for the database)
void fnA() {
fnB().then((_) {
// Here, all keys should have been loaded
});
}
Future fnB() {
return _db.open().then((_) {
return _db.keys().forEach((String key_name) {
return _db.getByKey(key_name).then((String data) {
// do something with data
return data;
});
});
});
}
解决方案
I made some improvments but haven't tested the code:
void fnA() {
fnB().then((_) {
// Here, all keys should have been loaded
});
}
Future fnB() {
return _db.open().then((_) {
List<Future> futures = [];
return _db.keys().forEach((String key_name) {
futures.add(_db.getByKey(key_name).then((String data) {
// do something with data
return data;
}));
}).then(() => Future.wait(futures));
});
}
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