[英]Getting value from function with callback parameters
Im trying to append the value I get in console log, to an array, but I keep getting undefined. 我试图将在控制台日志中获得的值附加到数组中,但我一直未定义。 I think the function is asynchronous thats why when i try to access it's undefined at time of execution. 我认为该函数是异步的,这就是为什么当我尝试访问它时在执行时是未定义的。 From what I understand from documentation is that its function parameters is a callback parameter, can someone tell me how to use the value I get to append to an array or a dict. 据我从文档中了解到的是,它的函数参数是一个回调参数,有人可以告诉我如何使用我要附加到数组或字典上的值。
var theparam = new ROSLIB.Param({
ros : ros,
name : formid.elements[i].name
});
theparam.get(function(value) {
console.log(value)
});
you can just add the value from the callback function to your array, when the function is invoked. 您可以在调用函数时将回调函数中的值添加到数组中。 May look so: 可能看起来像这样:
var myArray = [];
theparam.get(function(value) {
myArray.push(value);
});
console.log(myArray);
Edit: Ah that's because the console-log is processed before the actual .push is done (unsynchronized). 编辑:啊,这是因为在完成实际的.push(未同步)之前已处理了控制台日志。 Try to put the further processing code into the callback function like: 尝试将进一步的处理代码放入回调函数中,例如:
theparam.get(function(value) {
myArray.push(value);
console.log(myArray);
//Further code here
});
Edit with async loop: 使用异步循环进行编辑:
function asyncLoop(iterations, func, callback)
{
var index = 0;
var done = false;
var loop = null;
loop =
{
next: function()
{
if (done)
{
return;
}
if (index < iterations)
{
index++;
func(loop);
} else
{
done = true;
callback();
}
;
},
iteration: function()
{
return index - 1;
},
// break: function()
// {
// done = true;
// callback();
// }
};
loop.next();
return loop;
} }
And you can use it like: 您可以像这样使用它:
asyncLoop(iterations, function(loop)
{
//Iterations here
theParam.get(function(value)
{
myArray.push(value);
loop.next();
});
}, function()
{
//Finished loop
callback();
});
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