So, I get some JSON values from the server but I don't know if there will be a particular field or not.
So like:
{ "regatta_name":"ProbaRegatta",
"country":"Congo",
"status":"invited"
}
And sometimes, there will be an extra field like:
{ "regatta_name":"ProbaRegatta",
"country":"Congo",
"status":"invited",
"club":"somevalue"
}
I would like to check if the field named "club" exists so that at parsing I won't get
org.json.JSONException: No value for club
JSONObject class has a method named "has":
http://developer.android.com/reference/org/json/JSONObject.html#has(java.lang.String)
Returns true if this object has a mapping for name. The mapping may be NULL.
You can check this way where 'HAS' - Returns true if this object has a mapping for name. The mapping may be NULL.
if (json.has("status")) {
String status = json.getString("status"));
}
if (json.has("club")) {
String club = json.getString("club"));
}
You can also check using 'isNull' - Returns true if this object has no
mapping for name or if it has a mapping whose value is NULL.
if (!json.isNull("club"))
String club = json.getString("club"));
you could JSONObject#has, providing the key as input and check if the method returns true or false. You could also
use optString instead of getString:
Returns the value mapped by name if it exists, coercing it if
necessary. Returns the empty string if no such mapping exists
just before read key check it like before read
JSONObject json_obj=new JSONObject(yourjsonstr);
if(!json_obj.isNull("club"))
{
//it's contain value to be read operation
}
else
{
//it's not contain key club or isnull so do this operation here
}
isNull function definition
Returns true if this object has no mapping for name or
if it has a mapping whose value is NULL.
official documentation below link for isNull function
http://developer.android.com/reference/org/json/JSONObject.html#isNull(java.lang.String)
You can use has
public boolean has(String key)
Determine if the JSONObject contains a specific key.
Example
JSONObject JsonObj = new JSONObject(Your_API_STRING); //JSONObject is an unordered collection of name/value pairs
if (JsonObj.has("address")) {
//Checking address Key Present or not
String get_address = JsonObj .getString("address"); // Present Key
}
else {
//Do Your Staff
}
A better way, instead of using a conditional like:
if (json.has("club")) {
String club = json.getString("club"));
}
is to simply use the existing method optString(), like this:
String club = json.optString("club);
the optString("key") method will return an empty String if the key does not exist and won't, therefore, throw you an exception.
Try this:
let json=yourJson
if(json.hasOwnProperty(yourKey)){
value=json[yourKey]
}
Json has a method called containsKey().
You can use it to check if a certain key is contained in the Json set.
File jsonInputFile = new File("jsonFile.json");
InputStream is = new FileInputStream(jsonInputFile);
JsonReader reader = Json.createReader(is);
JsonObject frameObj = reader.readObject();
reader.close();
if frameObj.containsKey("person") {
//Do stuff
}
Try this
if(!jsonObj.isNull("club")){
jsonObj.getString("club");
}
I used hasOwnProperty('club')
var myobj = { "regatta_name":"ProbaRegatta",
"country":"Congo",
"status":"invited"
};
if ( myobj.hasOwnProperty("club"))
// do something with club (will be false with above data)
var data = myobj.club;
if ( myobj.hasOwnProperty("status"))
// do something with the status field. (will be true with above ..)
var data = myobj.status;
works in all current browsers.
You can try this to check wether the key exists or not:
JSONObject object = new JSONObject(jsonfile);
if (object.containskey("key")) {
object.get("key");
//etc. etc.
}
I am just adding another thing, In case you just want to check whether anything is created in JSONObject or not you can use length(), because by default when JSONObject is initialized and no key is inserted, it just has empty braces {} and using has(String key) doesn't make any sense.
So you can directly write if (jsonObject.length() > 0) and do your things.
Happy learning!
You can use the JsonNode#hasNonNull(String fieldName), it mix the has method and the verification if it is a null value or not
Related
I’m a beginner in Laravel but have a problem at first. I wrote this query and I’m waiting for Sonya Bins as result but unexpectedly I see ["Sonya Bins"]. what’s the problem?
Route::get('products', function () {
$articles=DB::table('users')->where('id','2')->get()->pluck('name');
return view('products',compact('articles'));
});
pluck will return array if you want to get only single value then use value
// will return array
$articles=DB::table('users')->where('id','2')->get()->pluck('name');
//will return string
$articles=DB::table('users')->where('id','2')->value('name');
// output Sonya Bins
here is an example from the documentation:
if you don't even need an entire row, you may extract a single value from a record using the value method. This method will return the value of the column directly:
$email = DB::table('users')->where('name', 'John')->value('email');
Read more about it here
Hope it helps.
Thanks
pluck() used to return a String before Laravel 5.1, but now it returns an array.
The alternative for that behavior now is value()
Try this:
Route::get('products', function () {
$articles=DB::table('users')->where('id','2')->get()->value('name');
return view('products',compact('articles'));
});
I think it's easier to use the Model + find function + value function.
Route::get('products', function () {
$articles = User::find(2)->value('name');
return view('products',compact('articles'));
});
pluck will return the collection.
I think id is your primary key.
You can just get the first record, and call its attribute's name:
DB::table('users')->where('id','2')->first()->name;
or
DB::table('users')->find(2)->name;
First thing is that you used invalid name for what you pass to view - you don't pass articles but user name.
Second thing is that you use get method to get results instead of first (or find) - you probably expect there is only single user with id = 2.
So to sum up you should use:
$userName = DB::table('users')->find(2)->name;
return view('products',compact('userName'));
Of course above code is for case when you are 100% sure there is user with id = 2 in database. If it might happen there won't be such user, you should use construction like this:
$userName = optional(DB::table('users')->find(2))->name;
($userName will be null if there is no such record)
or
$userName = optional(DB::table('users')->find(2))->name ?? 'No user';
in case you want to use custom string.
The problem with the ECMA standard for sort of Object.keys() is known:
Object.keys() handle all keys with integer (example: 168), including integer as strings (example: "168"), as a integer. The result is, both are the same (168 === "168"), and overwrite itself.
var object = {};
object["168"] = 'x';
object[168] = 'y';
Object.keys(object); // Array [ "168" ]
object[Object.keys(object)]; // "y"
Interestingly, all keys (including pure integer keys) are returned as a string.
The ecma262 wrote about this: All keys will be handle as a integer, expect the key is a String but is not an array index.
https://tc39.es/ecma262/#sec-ordinaryownpropertykeys
That should tell us: 168 === "168". A toString() do not solve the problem.
var object = {};
object[[3].toString()] = 'z';
object[[1].toString()] = 'x';
object[[2].toString()] = 'y';
Object.keys(object);
// Array(3) [ "1", "2", "3" ]
Paradoxically, in this case, only integer apply as "enumerable" (it's ignoring array.sort(), that sort also strings with letters.).
My question about this is simple: How can i prevent the sort function in Object.keys()? I have testet the Object.defineProperties(object, 1, {value: "a", enumerable: true/false}), but that mean not realy enumerable in the case of integer or string or integer-like string. It means only should it be counted with or not. It means "counted" like omit (if it false), not "enumerabled" like ascending or descending.
A answere like that is not a good answer: Please use only letters [a-zA-Z] or leastwise a letter at the first position of keyword.
What I want: That the keys are not sorted, but output in the order in which they were entered, whether integer, string or symbol.
Disclaimer: Please solutions only in JavaScript.
Javascript Objects are unordered by their nature. If you need an ordered object-like variable I would suggest using a map.
To achieve what you're looking for with a map instead of object you'd do something like the below:
var map1 = new Map();
map1.set("123", "c");
map1.set(123, "b");
var iterator1 = map1.keys();
var myarray = [];
for (var i = 0; i < map1.size; i++) {
myarray.push(iterator1.next().value);
}
console.log(myarray);
// Array ["123", 123]
Unfortunately it's not compatible with IE and I'm not sure how else you could achieve what you need without it. A quick Google did return something about jQuery maps, though.
If you don't want to use jQuery and still need to support IE some points are below:
Is there anything stopping you using an array rather than JS object to store the data you need? This will retain the order per your requirements unlike objects. You could have an object entry in each iteration which represents the key then use a traditional foreach to obtain them as an array. I.e.
The array:
var test_array = [
{key: 123, value: 'a value here'},
{key: "123", value: 'another value here'}
];
// console.log(test_array);
Getting the keys:
var test_array_keys = [];
test_array.forEach(function(obj) { test_array_keys.push(obj['key']); } );
// console.log(test_array_keys);
Then if you needed to check whether the key exists before adding a new entry (to prevent duplicates) you could do:
function key_exists(key, array)
{
return array.indexOf(key) !== -1;
}
if(key_exists('12345', test_array_keys))
{
// won't get here, this is just for example
console.log('Key 12345 exists in array');
}
else if(key_exists('123', test_array_keys))
{
console.log('Key 123 exists in array');
}
Would that work? If not then the only other suggestion would be keeping a separate array alongside the object which tracks the keys and is updated when an entry is added or removed to/from the object.
Object Keys sorted and store in array
First Creating student Object. then sort by key in object,last keys to store in array
const student={tamil:100, english:55, sci:85,soc:57}
const sortobj =Object.fromEntries(Object.entries(student).sort())
console.log(Object.keys(sortobj))
use map instead of an object.
let map = new Map()
map.set("a", 5)
map.set("d", 6)
map.set("b", 12)
to sort the keys (for example, to update a chart data)
let newMap = new Map([...map.entries()].sort())
let keys = Array.from(newMap.keys()) // ['a','b','d']
let values = Array.from(newMap.values()) // [5,12,6]
trying to return string builder in a loop. is this workable.. I am collecting a list with each(), then appending 'it' to "scriptBldr_" to create a different object name each time to hold the string. then I collect the object names in a list. And trying to return using a for loop for each object name. But it's failing.
List.each {
String builderstring = "scriptBldr_" + it.replaceAll (/"/, '')
StringBuilder $builderstring = StringBuilder.newInstance()
if (ValidUDA == "Region") {
$builderstring <<"""
XYZCode
"""
StringBuilders.add(builderstring)
}
}
for(item in StringBuilders)
{
return item
}
I guess the following code does what you intended to code:
def myList = ['Hello "World"', 'asb"r"sd']
def ValidUDA = "Region"
def builders = [:]
myList.each {
String builderstring = "scriptBldr_" + it.replaceAll (/"/, '')
builders[builderstring] = StringBuilder.newInstance()
if (ValidUDA == "Region") {
builders[builderstring] <<"""
XYZCode
"""
}
}
return builders
A return statement will immediatly return from the method and hence will exit the loop and only called once. So, I guess, what you wanted to achieve is to return a list of StrinngBuilders.
some hints:
it is unusual in Groovy to start a variable with $ and you can run into problems with such a naming
when asking a question on SO, try to come up with a working example. As you can see, you example was missing some definitions
Update: as you've stated in you comment that you tryed to create dynamic variable names, I've updated the code to use maps. The returned map now contains the StringBuilders together with their names.
I have an array of subscription instances #subscription_valids and an array of subscribed player that look like that :
array_subscribed_players = [{"name0" => "link1"}, {"name1"=>"link2"}, {"name2"=>"link3"}....]
What I need to do is : for each subscription in #subscription_valids :
#subscription_valids.each do |subscription|
I need to check if subscription.user.full_name or if subscription.user.full_name_inversed matches a key in one of the hashes of array_subscribed_player (in the exemple "name0", "name1" or "name2").
If it matches then I should store the relevant subscription as key in a hash in a new array and extract the relevant link as value of this hash. My final outpout should be an array that looks like this :
[{subscription1 => "link1"}, {subscription2 => "link2}, ...]
else if the subscription.user.full_name doesnt match i'll just store the subscription in a failure array.
How can I achieve this result ?
See http://ruby-doc.org/core-2.2.3/Hash.html
A user-defined class may be used as a hash key if the hash and eql?
methods are overridden to provide meaningful behavior. By default,
separate instances refer to separate hash keys.
so I think you should override your .eql? method in #subscription_valids to something meaningful (like a unique string)
I can't think for a Array method so you can go like:
demo
results = []
failures = []
#subscription_valids.each do |subscription|
array_subscribed_players.each do |player|
if player.keys.first == subscription.user.full_name || player.keys.first == subscription.user.full_name_inversed
results << { subscription => player[player.keys.first] }
else
failures << subscription
end
end
end
You can try the following:
valid = array_subscribed_players.select{|x| #subscription_valids.map(&:name).include?(x.keys.first)}
Demo
If you need to store both valid and invalid values somewhere:
valid, invalid = array_subscribed_players.partition{|x| #subscription_valids.map(&:name).include?(x.keys.first)}
Some background on the issue. From the front end, I have two select boxes with the multiple property. One box is for approved items, the other is for ignored items. I place these into a Map with the key being the company's UID, and the value either being "Y" or "N" depending on which box the UID is in. Inserting HashMap Values to a table using ibatis provided some assistance, but the answer involved manually putting the entries, where as I am dynamically creating the map, so not sure what the keys will be. Below is the code for the Java:
// Set up the map object for the back end
Map<Integer, String> posMap = new HashMap<Integer, String>();
// Get the approved mailers
String[] mailerList = request.getParameterValues("approved");
if (mailerList != null && mailerList.length > 0)
{
for(String mailer : mailerList)
{
posMap.put(Integer.parseInt(mailer), "Y");
}
}
// reset the mailerList
mailerList = null;
// get the ignored mailers
mailerList = request.getParameterValues("ignored");
if (mailerList != null && mailerList.length > 0)
{
for(String mailer : mailerList)
{
posSampleMap.put(Integer.parseInt(mailer), "N");
}
}
// only update POS if the map is not empty
if(!posMap.isEmpty())
{
updateMapper.updatePOSSampling(posMap);
}
Normally, I would have something like this in the mapper.xml file:
<update id="updatePOSSampling" parameterType="hashmap">
UPDATE <table_name>
SET sampling_enabled = ${myMapValue}
WHERE mailer_name = ${myMapKey}
</update>
In the link I provided, they were manually putting in the keys and values, and as such, the example IBATIS could refer to the key. Since I'm not sure what my key is, what would be the best way to generate this query? I've got a temporary workaround of sending a two dimension array, but I feel using a Map DO would be a better way. Thanks in advance for any assistance.