After making a REST request, I want to check if the ListView dataSource has received data. My code looks to something like
if(this.state.dataSource.length == 0){
return (
<Text> No data </Text>
);
I always get an error telling me that this.state.dataSource.length is undefined. You can find a minimal example in this snack.
You can do it like :
if ( this.state.dataSource && this.state.dataSource.length == 0 ) {
// your code
}
You want to make sure this.state.dataSource has been initialized to an empty array when your component is created. That way, this.state.dataSource.length === 0 will be true until your data is fetched.
Related
Probably a noob Question: On my server, there is a filter which returns all available options if an array of the filter object has length.0 for certain options.
Now if say i have an input "All Options" from the user side, this option when clicked must somehow tell the array to have length.0, so the server returns all options .
I tried to set the Input to
<mat-option [value]= null >Alle</mat-option>
But that results in an array that has the value null instead of no length at all.
I also tried
If (data.array[1] == undefined){
data.array.length == 0
}
But that did not work
Leave the value to null and then do it like this:
if (!data.array) {
data.array = [];
}
I am using reactJS and I am using some conditions to show my components. The code below is properly working. It show my success message without any problem. The FINALMESSAGE.showFinalMessage = true and FORMSTATUS["loadingForm"] = false
{FINALMESSAGE.showFinalMessage && !FORMSTATUS["loadingForm"] && <FinalMessageSave></FinalMessageSave>}
But when I add a condition with string like this:
{FINALMESSAGE.showFinalMessage && FINALMESSAGE.finalMessageStatus === "SUCCESS" && !FORMSTATUS["loadingForm"] && <FinalMessageSave ></FinalMessageSave>}
it doesnt work anymore even the FINALMESSAGE.showFinalMessage = "SUCCESS"
Here is the screenshot of my state
I'm trying to process an array of JSON objects that have various common attributes, filtering each array entry on one or more of those attributes.
Normally, I'd just do it something like this:
let filteredResultsArray = originalArray.filter((obj) => {
return obj.attribute1 <= 3 && obj.attribute2 > 0 && obj.attribute3 === 10;
});
My problem is that the filter parameters (the part after "return" in the code above) are highly variable (and unpredictable) from run to run, so I can't hard-code them in the filter. I compute them on the fly and store the whole thing in a string in my code. For example, on one run it might be:
myAttributeString = "obj.attribute1 <= 3 && obj.attribute2 > 0 && obj.attribute3 === 10";
I've tried doing this:
let filteredResultsArray = originalArray.filter((obj) => {
return myAttributeString;
});
That's failing to filter anything. Apparently .filter() is not properly interpreting what I've stored in myAttributeString as filter criteria.
I have a sneaking suspicion that eval(myAttributeString) might be one way to pull this off, but unfortunately I'm working on a team where we've got tslint set to disallow the use of eval(), so that's not an option.
Anybody have an idea how I can get this to work?
When you "compute them on the fly", instead of creating a string, create a callback function that you can then pass to filter. For example, instead of
const myAttributeString = "obj.attribute1 <= 3 && obj.attribute2 > 0 && obj.attribute3 === 10";
do
const filterCallback = obj => obj.attribute1 <= 3 && obj.attribute2 > 0 && obj.attribute3 === 10
Then, later, when the appropriate time comes to .filter, simply pass that as the callback:
const filteredResultsArray = originalArray.filter(filterCallback);
If you can't pass functions around, another option would be to build an array of conditions, for example
[
{
prop: "attribute1",
constraint: "<=",
value: 3
},
{
prop: "attribute2",
constraint: ">",
value: 0
},
// ...
]
and then turn the object into the filter function needed.
****************************************UPDATE******************************
As I suspected, eval() did work, but since I can't use it in my delivered code, and thanks to CertainPerformance's suggestion (which put my thinking on the right track) as well as the Node.js documentation site (via a lucky Google search), I was able to find a workaround using the vm module:
import * as vm from "vm";
let filteredResultsArray = originalArray.filter(
vm.runInThisContext("(obj) => {
return " + myAttributeString + ";}"));
Case closed.
I want to set flash message if there's not fullfilled row "surname" in database. How can I check if row surname is null ?
I tried to make something like this:
if(!isset(['User']['surname'])
or
if($user(['User']['surname']) === NULL
it obviously doesnt work
You can check it like.
<?php
if(!isset($user['User']['surname']) || empty($user['User']['surename'])){
// your code goes here
}
if(empty($user['User']['surname'])) {
// your code goes here
}
you can check like this
if(isset($user['surname']) || empty($user['surname'])){
$this->Session->setFlash('No Data.');
}
I want to update one column which is an INT with a NULL value. I'm using CakePHP 2.3 with the saveField('field', 'value') method.
Here is my code :
$this->Customer->id = $customer_id;
if ($this->Customer->saveField('account_id', 'NULL')) {
//Do some stuff
}
So when I put 'NULL', the row is updated to 0. I tried NULL without quotes and the row is not updated.
EDIT :
The field in the db accepts NULL value.
Do you have any idea ?
Thanks
Do not pass 'NULL' as a string but as null value:
if($this->Customer->saveField('account_id', null))
{
//do some stuff
}
else
{
//do you get anything here ?
debug($this->Customer->validationErrors);
}
I've had a similiar problem caused by a Upload Behaviour that had validations preventing the saving. Check your models, it might help. I assume saveField returns true even when validation rules prevent saving.