How to Remove Single Object in Array from Multiple Matching Object

How to remove single object in array from multiple matching object

Swift 2

Solution when using a simple Swift array:

var myArray = [1, 2, 2, 3, 4, 3]

if let index = myArray.indexOf(2) {
    myArray.removeAtIndex(index)
}

It works because .indexOf only returns the first occurence of the found object, as an Optional (it will be nil if object not found).

It works a bit differently if you're using NSMutableArray:

let nsarr = NSMutableArray(array: [1, 2, 2, 3, 4, 3])
let index = nsarr.indexOfObject(2)
if index < Int.max {
    nsarr.removeObjectAtIndex(index)
}

Here .indexOfObject will return Int.max when failing to find an object at this index, so we check for this specific error before removing the object.

Swift 3

The syntax has changed but the idea is the same.

Array:

var myArray = [1, 2, 2, 3, 4, 3]
if let index = myArray.index(of: 2) {
    myArray.remove(at: index)
}
myArray // [1, 2, 3, 4, 3]

NSMutableArray:

let myArray = NSMutableArray(array: [1, 2, 2, 3, 4, 3])
let index = myArray.index(of: 2)
if index < Int.max {
    myArray.removeObject(at: index)
}
myArray // [1, 2, 3, 4, 3]

In Swift 3 we call index(of:) on both Array and NSMutableArray, but they still behave differently for different collection types, like indexOf and indexOfObject did in Swift 2.

Remove one object from an array with multiple matching objects

I think you have an XY-problem. Instead of an array, you should use a hash with number of occurrences as the value.

hash = Hash.new(0)

When you want to add an entity, you should do:

hash["a"] += 1

If you want to limit the number to a certain value, say k, then do:

hash["a"] += 1 unless hash["a"] == k

remove objects from array by object property

I assume you used splice something like this?

for (var i = 0; i < arrayOfObjects.length; i++) {
    var obj = arrayOfObjects[i];

    if (listToDelete.indexOf(obj.id) !== -1) {
        arrayOfObjects.splice(i, 1);
    }
}

All you need to do to fix the bug is decrement i for the next time around, then (and looping backwards is also an option):

for (var i = 0; i < arrayOfObjects.length; i++) {
    var obj = arrayOfObjects[i];

    if (listToDelete.indexOf(obj.id) !== -1) {
        arrayOfObjects.splice(i, 1);
        i--;
    }
}

To avoid linear-time deletions, you can write array elements you want to keep over the array:

var end = 0;

for (var i = 0; i < arrayOfObjects.length; i++) {
    var obj = arrayOfObjects[i];

    if (listToDelete.indexOf(obj.id) === -1) {
        arrayOfObjects[end++] = obj;
    }
}

arrayOfObjects.length = end;

and to avoid linear-time lookups in a modern runtime, you can use a hash set:

const setToDelete = new Set(listToDelete);
let end = 0;

for (let i = 0; i < arrayOfObjects.length; i++) {
    const obj = arrayOfObjects[i];

    if (setToDelete.has(obj.id)) {
        arrayOfObjects[end++] = obj;
    }
}

arrayOfObjects.length = end;

which can be wrapped up in a nice function:

const filterInPlace = (array, predicate) => {    let end = 0;
    for (let i = 0; i < array.length; i++) {        const obj = array[i];
        if (predicate(obj)) {            array[end++] = obj;        }    }
    array.length = end;};
const toDelete = new Set(['abc', 'efg']);
const arrayOfObjects = [{id: 'abc', name: 'oh'},                        {id: 'efg', name: 'em'},                        {id: 'hij', name: 'ge'}];
filterInPlace(arrayOfObjects, obj => !toDelete.has(obj.id));console.log(arrayOfObjects);

How to remove object from array except matching value?

You may use Array.filter along with Array.includes:

var items = [{"id":"88","name":"Lets go testing"},{"id":"99","name":"Have fun boys and girls"},{"id":"108","name":"You are awesome!"}];var arr = ["88", "108"];
const result = items.filter(item => arr.includes(item.id));console.log(result);

How to remove object if object matches

One way is to use Array#filter with Array#some + JSON.stringify() for comparison.

Note that Array#filter returns a new array. So the variable needs to be reassigned.

let originalArray = [
  {name: 'abc', country: 'eng'},
  {name: 'xyz', country: 'ind'},
  {name: 'pqr', country: 'us'}
];

let objectToBeRemove = [
  {name: 'pqr', country: 'us'}
];

originalArray = originalArray.filter(obj => 
  objectToBeRemove.some(objToRemove => 
    JSON.stringify(objToRemove) !== JSON.stringify(obj)
  )
);

console.log(originalArray);

How do I remove an object from an array with a matching property?

You could use Array#filter method:

food = {
  id: 1,
  name: 'Pizza',
  price: 16
};

orders = [
  { food_id: 2, table_id: 5 },
  { food_id: 2, table_id: 5 },
  { food_id: 1, table_id: 5 },
  { food_id: 3, table_id: 5 },
  { food_id: 1, table_id: 5 }
];

removeFoodOrder(food: Food): void {
  this.orders = this.orders.filter(({ food_id }) => food_id !== food.id);        
}

Edit:

Since your array allows duplicate elements and you want to remove only the first match, you could use the Array#findIndex + Array#filter methods:

const foundIndex = this.orders.findIndex(({ food_id }) => food_id === food.id);
this.orders = this.orders.filter((_, index) => index !== foundIndex);

Remove matched object from deeply nested array of objects

If you don't mind modifying the parameter tree in-place, this should do the job. Note that it'll return null if you attempt to remove the root.

const tree = { id: 1, name: "Dog", parent_id: null, children: [ { id: 2, name: "Food", parent_id: 1, children: [] }, { id: 3, name: "Water", parent_id: 1, children: [ { id: 4, name: "Bowl", parent_id: 3, children: [] }, { id: 5, name: "Oxygen", parent_id: 3, children: [] }, { id: 6, name: "Hydrogen", parent_id: 3, children: [] } ] } ] };
const removeFromTree = (root, nameToDelete, parent, idx) => {  if (root.name === nameToDelete) {    if (parent) {      parent.children.splice(idx, 1);    }    else return null;  }    for (const [i, e] of root.children.entries()) {    removeFromTree(e, nameToDelete, root, i);  }    return tree;};
console.log(removeFromTree(tree, "Oxygen"));

Lodash Remove objects from array by matching ids array

As you mentioned you need the _.remove method and the specific condition you mention is whether the removeItem array contains the id of the checked element of the array.

var removeElements = _.remove(a, obj => removeItem.includes(obj.id));
// you only need to assign the result if you want to do something with the removed elements.
// the a variable now holds the remaining array

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