I don't know if vue recognize the syntax below:
if(var error = errors.description){
location.href = "/redirect?topic="+error;
}
The code above returns a compilation error:
ERROR in ./resources/js/forms/Signup.vue?vue&type=script&lang=js& (./node_modules/babel-loader/lib??ref--4-0!./node_modules/vue-loader/lib??vue-loader-options!./resources/js/forms/Signup.vue?vue&type=script&lang=js&)
Someone knows how to assign a variable inside the if else condition?
This is rather a JavaScript syntax issue than Vue. While I highly recommend not assigning within a conditional, you can do so only by either declaring the variable earlier or not explicitly declaring it at all, i.e. by removing the var above.
Here's an example with your above code:
if(error = errors.description){
location.href = "/redirect?topic="+error;
}
To be clear, it is highly recommended not to do the above, or at the very least declare var error earlier so that you don't accidentally modify a global variable, like so:
let error;
if(error = errors.description){
location.href = "/redirect?topic="+error;
}
Of course the most explicit and safe solution to avoid confusion about the assignment is to simply do it earlier:
let error = errors.description;
if (error) {
location.href = "/redirect?topic="+error;
}
There has been some discussion about whether assignment within conditionals is good practice. However, on a completely separate note it is widely agreed that assigning variables that haven't been declared with var, let, or const is dangerous as you could accidentally modify variables of higher scope.
Related
we know all this problem, and know how to solve it.
But I have an stranger Error in this context where I could use a good hint:
this.getData(id)
.then((response) => {
this.root.basic.selected.num = response.data.number; // number
this.root.basic.selected.date = response.data.date; // Date
this.root.basic.selected.text = response.data.text; // String. <- There is the error
}
})
The selected Object is bound by the "makeAutoObserveable()" Nothing special here. But a lot of code to push it all here.
Why this error happens only on the .text setter not on the others?
Is this a possible known behavior?
I solved it with "runInAction()" but I would like to understand the reason.
Kind Regards
Gregor
I want to create a Developer Variable to the workspace in Blockly, but I cannot find the necessary function/method.
I do not want to create the variable over a button. The variable should be included even if there is no block in the workspace.
With these two functions I can get the already created variables:
var variables = workspace.getAllVariables();
var dev_var = Blockly.Variables.allDeveloperVariables(workspace);
But what is the setting function?
Developer variables are variables that will never be visible to the user, but will exist in the generated code. If that's what you're looking for: there's no API for it, but here are some things you can do.
If you want to reserve the name so that users can't accidentally override your variable, call yourGenerator.addReservedWords('var1,var2,...'). You can initialize the variable in your wrapper code.
If you really want Blockly to both reserve and declare the variable for you, you could override the init function on your generator.
On the other hand, if what you want is a user-visible variable that always shows up in the toolbox, without the user creating it, you should call yourWorkspace.createVariable('variable_name').
The unit test blocks all assume that the variable unittestResults exists and can be written to. To indicate this, the block definition includes the function getDeveloperVars, which returns an array of strings. Each string is a variable name.Follow this issue in gtihub
Blockly.Blocks['unittest_fail'] = {
// Always assert an error.
init: function() {
this.setColour(65);
this.setPreviousStatement(true);
this.setNextStatement(true);
this.appendDummyInput()
.appendField(new Blockly.FieldTextInput('test name'), 'MESSAGE')
.appendField('fail');
this.setTooltip('Records an error.');
},
getDeveloperVars: function() {
return ['unittestResults'];
}
};
LINK : https://github.com/google/blockly/issues/1535
I have below code to create column:
DTColumnBuilder.newColumn(null).withTitle('Validation').renderWith(validationRenderer)
and render function:
function validationRenderer(data, type, full, meta) {
.......
}
Now, I want to pass custom parameters to validationRenderer so that I can access it inside the function, like below:
DTColumnBuilder.newColumn(null).withTitle('Validation').renderWith(validationRenderer('abc'))
function validationRenderer(data, type, full, meta, additionalParam) {
// do something with additionalParam
}
I could not find it in the documentation but there must be something to pass additional parameters in meta as per the reference from here
Yes, you can. Or, better, you technically can, but you may use a clever workaround to handle your issue.
I had this issue today, and found a pretty sad (but working) solution.
Basically, the big problem is that the render function is a parameter passed to the datatable handler, which is (of course) isolated.
In my case, to make a pratical example, I had to add several dynamic buttons, each with a different action, to a dynamic datatable.
Apparently, there was no solution, until I thought the following: the problem seems to be that the renderer function scope is somewhat isolated and unaccessible. However, since the "return" of the function is called only when the datatable effectively renders the field, you may wrap the render function in a custom self-invoking-anonymous-function, providing arguments there to use them once the cell is being rendered.
Here is what I did with my practical example, considering the following points:
The goal was to pass the ID field of each row to several different custom functions, so the problem was passing the ID of the button to call when the button is effectively clicked (since you can't get any external reference of it when it is rendered).
I'm using a custom class, which is the following:
hxDatatableDynamicButton = function(label, onClick, classNames) {
this.label = label;
this.onClick = onClick;
this.classNames = this.classNames || 'col5p text-center';
}
Basically, it just creates an instance that I'm later using.
In this case, consider having an array of 2 different instances of these, one having a "test" label, and the other one having a "test2" label.
I'm injecting these instances through a for loop, hence I need to pass the "i" to my datatable to know which of the buttons is being pressed.
Since the code is actually quite big (the codebase is huge), here is the relevant snippet that you need to accomplish the trick:
scope.datatableAdditionalActionButtons.reverse();
scope._abstractDynamicClick = function(id, localReferenceID) {
scope.datatableAdditionalActionButtons[localReferenceID].onClick.call(null, id);
};
for (var i = 0; i < scope.datatableAdditionalActionButtons.length; i++) {
var _localReference = scope.datatableAdditionalActionButtons[i];
var hax = (function(i){
var _tmp = function (data, type, full, meta) {
var _label = scope.datatableAdditionalActionButtons[i].label;
return '<button class="btn btn-default" ng-click="_abstractDynamicClick('+full.id+', '+i+')">'+_label+'</button>';
}
return _tmp;
})(i);
dtColumns.unshift(DTColumnBuilder.newColumn(null).notSortable().renderWith(hax).withClass(_localReference.classNames));
}
So, where is the trick? the trick is entirely in the hax function, and here is why it works: instead of passing the regular renderWith function prototype, we are using a "custom" render, which has the same arguments (hence same parameters) as the default one. However, it is isolated in a self invoking anonymous function, which allows us to arbitrarely inject a parameter inside it and, so, allows us to distinguish, when rendering, which "i" it effectively is, since the isolated scope of the function is never lost in this case.
Basically, the output is as follow:
And the inspection actually shows that elements are effectively rendered differently, hence each "i" is being rendered properly, while it wouldn't have if the function wouldn't have been wrapped in a self invoking anonymous function:
So, basically, in your case, you would do something like this:
var _myValidator = (function(myAbcParam){
var _validate = function (data, type, full, meta) {
console.log("additional param is: ", myAbcParam); // logs "abc"
return '<button id="'+myAbcParam+'">Hello!</button>'; // <-- renders id ="abc"
}
return _validate ;
})('abc');
DTColumnBuilder.newColumn(null).withTitle('Validation').renderWith(_myValidator);
// <-- note that _myValidator is passed instead of "_myValidator()", since it is already executed and already returns a function.
I know this is not exactly the answer someone may be expecting, but if you need to accomplish something that complex in datatable it really looks like the only possible way to do this is using a self invoking anonymous function.
Hope this helps someone who is still having issues with this.
Is there a convention for variable naming in cases like the following? I find myself having to have two names, one the optional and one for the unwrapped.
let user = match optional_user {
Some(u) => {
u
}
None => {
new("guest", "guest").unwrap()
}
};
I'm unsure if there is a convention per say, but I often see (and use) maybe for Options. i.e.
let maybe_thing: Option<Thing> = ...
let thing: Thing = ...
Also, in regards to your use of u and user in this situation, it is fine to use user in both places. i.e.
let user = match maybe_user {
Some(user) => user,
...
This is because the match expression will be evaluated prior to the let assignment.
However (slightly off topic) #Manishearth is correct, in this case it would be nicer to use or_else. i.e.
let user = maybe_user.or_else(|| new("guest", "guest")).unwrap();
I'd recommend becoming familiar with the rest of Option's methods too as they are excellent for reducing match boilerplate.
If you're going to use a variable to initialize another and you don't need to use the first variable anymore, you can use the same name for both variables.
let user = /* something that returns Option<?> */;
let user = match user {
Some(u) => {
u
}
None => {
new("guest", "guest").unwrap()
}
};
In the initializer for the second let binding, the identifier user resolves to the first user variable, rather than the one being defined, because that one is not initialized yet. Variables defined in a let statement only enter the scope after the whole let statement. The second user variable shadows the first user variable for the rest of the block, though.
You can also use this trick to turn a mutable variable into an immutable variable:
let mut m = HashMap::new();
/* fill m */
let m = m; // freeze m
Here, the second let doesn't have the mut keyword, so m is no longer mutable. Since it's also shadowing m, you no longer have mutable access to m (though you can still add a let mut later on to make it mutable again).
Firstly, your match block can be replaced by optional_user.or_else(|| new("guest", "guest")).unwrap()
Usually for destructures where the destructured variable isn't used in a large block, a short name like u is common. However it would be better to call it user if the block was larger with many statements.
I've been working on this script for about two hours straight and I can't figure out what I'm doing wrong. I've never used variables in jquery before, and all of the guides I'm reading show variables but not used in any useful context. Here is my code:
var $a = 1;
var $b = 1;
$('#pdnav1').click(function(){
if($a == $b) {
var $a = 0;
$('#pdbgimg').html('<img id="pdimg" src="http://royalty-ro.com/forums/uploads/images/1303326955-U1.jpg">');
$('#pd1').fadeIn(0);
$('#pdbg1').animate({top: '0px'});
}else{
var $a = 1;
$('.pdhide').animate({
top: '-200px'
});
$('.pdhide2').delay(400).fadeOut(0);
}
});
Mainly all I want to to do is the "if" statement the first time I click it, and then the "else" statement the next time (repeating this process each time you click it, just like a toggle).
You are declaring a $a variable inside your function :
var $a = 0;
That declaration, inside the function, overrides the global $a variable that's defined outside of the function.
If you want to use global variables, and access them inside functions, don't re-define them using var inside that function.
For more informations, you should read about Variable Scope.
And, btw : using $ in variables names is generally not quite considered as a good idea...