Nik Collection 2 By DxO 2.3.0 CR2
Hien Mondesir
The Illuminate\Support\Collection class provides a fluent, convenient wrapper for working with arrays of data. For example, check out the following code. We'll use the collect helper to create a new collection instance from the array, run the strtoupper function on each element, and then remove all empty elements:
As you can see, the Collection class allows you to chain its methods to perform fluent mapping and reducing of the underlying array. In general, collections are immutable, meaning every Collection method returns an entirely new Collection instance.
Collections are "macroable", which allows you to add additional methods to the Collection class at run time. The Illuminate\Support\Collection class' macro method accepts a closure that will be executed when your macro is called. The macro closure may access the collection's other methods via $this, just as if it were a real method of the collection class. For example, the following code adds a toUpper method to the Collection class:
For the majority of the remaining collection documentation, we'll discuss each method available on the Collection class. Remember, all of these methods may be chained to fluently manipulate the underlying array. Furthermore, almost every method returns a new Collection instance, allowing you to preserve the original copy of the collection when necessary:
The chunkWhile method breaks the collection into multiple, smaller collections based on the evaluation of the given callback. The $chunk variable passed to the closure may be used to inspect the previous element:
Note
The collect method is especially useful when you have an instance of Enumerable and need a non-lazy collection instance. Since collect() is part of the Enumerable contract, you can safely use it to get a Collection instance.
The contains method determines whether the collection contains a given item. You may pass a closure to the contains method to determine if an element exists in the collection matching a given truth test:
The countBy method counts the occurrences of values in the collection. By default, the method counts the occurrences of every element, allowing you to count certain "types" of elements in the collection:
The diff method compares the collection against another collection or a plain PHP array based on its values. This method will return the values in the original collection that are not present in the given collection:
The diffAssoc method compares the collection against another collection or a plain PHP array based on its keys and values. This method will return the key / value pairs in the original collection that are not present in the given collection:
The diffKeys method compares the collection against another collection or a plain PHP array based on its keys. This method will return the key / value pairs in the original collection that are not present in the given collection:
The doesntContain method determines whether the collection does not contain a given item. You may pass a closure to the doesntContain method to determine if an element does not exist in the collection matching a given truth test:
You may also call the firstOrFail method with no arguments to get the first element in the collection. If the collection is empty, an Illuminate\Support\ItemNotFoundException exception will be thrown:
The flatMap method iterates through the collection and passes each value to the given closure. The closure is free to modify the item and return it, thus forming a new collection of modified items. Then, the array is flattened by one level:
The forPage method returns a new collection containing the items that would be present on a given page number. The method accepts the page number as its first argument and the number of items to show per page as its second argument:
The implode method joins items in a collection. Its arguments depend on the type of items in the collection. If the collection contains arrays or objects, you should pass the key of the attributes you wish to join, and the "glue" string you wish to place between the values:
By converting the collection to a LazyCollection, we avoid having to allocate a ton of additional memory. Though the original collection still keeps its values in memory, the subsequent filters will not. Therefore, virtually no additional memory will be allocated when filtering the collection's results.
Warning
Like most other collection methods, map returns a new collection instance; it does not modify the collection it is called on. If you want to transform the original collection, use the transform method.
The mapSpread method iterates over the collection's items, passing each nested item value into the given closure. The closure is free to modify the item and return it, thus forming a new collection of modified items:
The mapToGroups method groups the collection's items by the given closure. The closure should return an associative array containing a single key / value pair, thus forming a new collection of grouped values:
The merge method merges the given array or collection with the original collection. If a string key in the given items matches a string key in the original collection, the given item's value will overwrite the value in the original collection:
The mergeRecursive method merges the given array or collection recursively with the original collection. If a string key in the given items matches a string key in the original collection, then the values for these keys are merged together into an array, and this is done recursively:
You may pass an integer to random to specify how many items you would like to randomly retrieve. A collection of items is always returned when explicitly passing the number of items you wish to receive:
The reduceSpread method reduces the collection to an array of values, passing the results of each iteration into the subsequent iteration. This method is similar to the reduce method; however, it can accept multiple initial values:
The replace method behaves similarly to merge; however, in addition to overwriting matching items that have string keys, the replace method will also overwrite items in the collection that have matching numeric keys:
If there are no elements in the collection that should be returned by the sole method, an \Illuminate\Collections\ItemNotFoundException exception will be thrown. If there is more than one element that should be returned, an \Illuminate\Collections\MultipleItemsFoundException will be thrown.
The sort method sorts the collection. The sorted collection keeps the original array keys, so in the following example we will use the values method to reset the keys to consecutively numbered indexes:
If your sorting needs are more advanced, you may pass a callback to sort with your own algorithm. Refer to the PHP documentation on uasort, which is what the collection's sort method calls utilizes internally.
The sortBy method sorts the collection by the given key. The sorted collection keeps the original array keys, so in the following example we will use the values method to reset the keys to consecutively numbered indexes:
If you would like to sort your collection by multiple attributes, you may pass an array of sort operations to the sortBy method. Each sort operation should be an array consisting of the attribute that you wish to sort by and the direction of the desired sort:
The tap method passes the collection to the given callback, allowing you to "tap" into the collection at a specific point and do something with the items while not affecting the collection itself. The collection is then returned by the tap method:
Warning
toArray also converts all of the collection's nested objects that are an instance of Arrayable to an array. If you want to get the raw array underlying the collection, use the all method instead.
The unique method returns all of the unique items in the collection. The returned collection keeps the original array keys, so in the following example we will use the values method to reset the keys to consecutively numbered indexes:
The when method will execute the given callback when the first argument given to the method evaluates to true. The collection instance and the first argument given to the when method will be provided to the closure:
Collections also provide support for "higher order messages", which are short-cuts for performing common actions on collections. The collection methods that provide higher order messages are: average, avg, contains, each, every, filter, first, flatMap, groupBy, keyBy, map, max, min, partition, reject, skipUntil, skipWhile, some, sortBy, sortByDesc, sum, takeUntil, takeWhile, and unique.
For example, imagine your application needs to process a multi-gigabyte log file while taking advantage of Laravel's collection methods to parse the logs. Instead of reading the entire file into memory at once, lazy collections may be used to keep only a small part of the file in memory at a given time:
Bags or multisets (unordered collections that may contain duplicate elements) should implement this interface directly. All general-purpose Collection implementation classes (which typically implement Collection indirectly through one of its subinterfaces) should provide two "standard" constructors: a void (no arguments) constructor, which creates an empty collection, and a constructor with a single argument of type Collection, which creates a new collection with the same elements as its argument. In effect, the latter constructor allows the user to copy any collection, producing an equivalent collection of the desired implementation type. There is no way to enforce this convention (as interfaces cannot contain constructors) but all of the general-purpose Collection implementations in the Java platform libraries comply. The "destructive" methods contained in this interface, that is, the methods that modify the collection on which they operate, are specified to throw UnsupportedOperationException if this collection does not support the operation. If this is the case, these methods may, but are not required to, throw an UnsupportedOperationException if the invocation would have no effect on the collection. For example, invoking the addAll(Collection) method on an unmodifiable collection may, but is not required to, throw the exception if the collection to be added is empty. Some collection implementations have restrictions on the elements that they may contain. For example, some implementations prohibit null elements, and some have restrictions on the types of their elements. Attempting to add an ineligible element throws an unchecked exception, typically NullPointerException or ClassCastException. Attempting to query the presence of an ineligible element may throw an exception, or it may simply return false; some implementations will exhibit the former behavior and some will exhibit the latter. More generally, attempting an operation on an ineligible element whose completion would not result in the insertion of an ineligible element into the collection may throw an exception or it may succeed, at the option of the implementation. Such exceptions are marked as "optional" in the specification for this interface. It is up to each collection to determine its own synchronization policy. In the absence of a stronger guarantee by the implementation, undefined behavior may result from the invocation of any method on a collection that is being mutated by another thread; this includes direct invocations, passing the collection to a method that might perform invocations, and using an existing iterator to examine the collection. Many methods in Collections Framework interfaces are defined in terms of the equals method. For example, the specification for the contains(Object o) method says: "returns true if and only if this collection contains at least one element e such that (o==null ? e==null : o.equals(e))." This specification should not be construed to imply that invoking Collection.contains with a non-null argument o will cause o.equals(e) to be invoked for any element e. Implementations are free to implement optimizations whereby the equals invocation is avoided, for example, by first comparing the hash codes of the two elements. (The Object.hashCode() specification guarantees that two objects with unequal hash codes cannot be equal.) More generally, implementations of the various Collections Framework interfaces are free to take advantage of the specified behavior of underlying Object methods wherever the implementor deems it appropriate. Some collection operations which perform recursive traversal of the collection may fail with an exception for self-referential instances where the collection directly or indirectly contains itself. This includes the clone(), equals(), hashCode() and toString() methods. Implementations may optionally handle the self-referential scenario, however most current implementations do not do so. This interface is a member of the Java Collections Framework.Implementation Requirements:The default method implementations (inherited or otherwise) do not apply any synchronization protocol. If a Collection implementation has a specific synchronization protocol, then it must override default implementations to apply that protocol.Since:1.2See Also:Set, List, Map, SortedSet, SortedMap, HashSet, TreeSet, ArrayList, LinkedList, Vector, Collections, Arrays, AbstractCollectionMethod SummaryAll Methods Instance Methods Abstract Methods Default Methods Modifier and TypeMethod and Descriptionbooleanadd(E e)Ensures that this collection contains the specified element (optional operation).booleanaddAll(Collection c)Returns true if this collection contains all of the elements in the specified collection.booleanequals(Object o)Compares the specified object with this collection for equality.inthashCode()Returns the hash code value for this collection.booleanisEmpty()Returns true if this collection contains no elements.Iteratoriterator()Returns an iterator over the elements in this collection.default StreamparallelStream()Returns a possibly parallel Stream with this collection as its source.booleanremove(Object o)Removes a single instance of the specified element from this collection, if it is present (optional operation).booleanremoveAll(Collection c)Removes all of this collection's elements that are also contained in the specified collection (optional operation).default booleanremoveIf(Predicate c)Retains only the elements in this collection that are contained in the specified collection (optional operation).intsize()Returns the number of elements in this collection.default Spliteratorspliterator()Creates a Spliterator over the elements in this collection.default Streamstream()Returns a sequential Stream with this collection as its source.Object[]toArray()Returns an array containing all of the elements in this collection. T[]toArray(T[] a)Returns an array containing all of the elements in this collection; the runtime type of the returned array is that of the specified array.Methods inherited from interface java.lang.IterableforEachMethod Detailsizeint size()Returns the number of elements in this collection. If this collection contains more than Integer.MAX_VALUE elements, returns Integer.MAX_VALUE.Returns:the number of elements in this collectionisEmptyboolean isEmpty()Returns true if this collection contains no elements.Returns:true if this collection contains no elementscontainsboolean contains(Object o)Returns true if this collection contains the specified element. More formally, returns true if and only if this collection contains at least one element e such that (o==null ? e==null : o.equals(e)).Parameters:o - element whose presence in this collection is to be testedReturns:true if this collection contains the specified elementThrows:ClassCastException - if the type of the specified element is incompatible with this collection (optional)NullPointerException - if the specified element is null and this collection does not permit null elements (optional)iteratorIterator iterator()Returns an iterator over the elements in this collection. There are no guarantees concerning the order in which the elements are returned (unless this collection is an instance of some class that provides a guarantee).Specified by:iterator in interface IterableReturns:an Iterator over the elements in this collectiontoArrayObject[] toArray()Returns an array containing all of the elements in this collection. If this collection makes any guarantees as to what order its elements are returned by its iterator, this method must return the elements in the same order. The returned array will be "safe" in that no references to it are maintained by this collection. (In other words, this method must allocate a new array even if this collection is backed by an array). The caller is thus free to modify the returned array. This method acts as bridge between array-based and collection-based APIs.Returns:an array containing all of the elements in this collectiontoArray T[] toArray(T[] a)Returns an array containing all of the elements in this collection; the runtime type of the returned array is that of the specified array. If the collection fits in the specified array, it is returned therein. Otherwise, a new array is allocated with the runtime type of the specified array and the size of this collection. If this collection fits in the specified array with room to spare (i.e., the array has more elements than this collection), the element in the array immediately following the end of the collection is set to null. (This is useful in determining the length of this collection only if the caller knows that this collection does not contain any null elements.) If this collection makes any guarantees as to what order its elements are returned by its iterator, this method must return the elements in the same order. Like the toArray() method, this method acts as bridge between array-based and collection-based APIs. Further, this method allows precise control over the runtime type of the output array, and may, under certain circumstances, be used to save allocation costs. Suppose x is a collection known to contain only strings. The following code can be used to dump the collection into a newly allocated array of String: String[] y = x.toArray(new String[0]); Note that toArray(new Object[0]) is identical in function to toArray().Type Parameters:T - the runtime type of the array to contain the collectionParameters:a - the array into which the elements of this collection are to be stored, if it is big enough; otherwise, a new array of the same runtime type is allocated for this purpose.Returns:an array containing all of the elements in this collectionThrows:ArrayStoreException - if the runtime type of the specified array is not a supertype of the runtime type of every element in this collectionNullPointerException - if the specified array is nulladdboolean add(E e)Ensures that this collection contains the specified element (optional operation). Returns true if this collection changed as a result of the call. (Returns false if this collection does not permit duplicates and already contains the specified element.) Collections that support this operation may place limitations on what elements may be added to this collection. In particular, some collections will refuse to add null elements, and others will impose restrictions on the type of elements that may be added. Collection classes should clearly specify in their documentation any restrictions on what elements may be added. If a collection refuses to add a particular element for any reason other than that it already contains the element, it must throw an exception (rather than returning false). This preserves the invariant that a collection always contains the specified element after this call returns.Parameters:e - element whose presence in this collection is to be ensuredReturns:true if this collection changed as a result of the callThrows:UnsupportedOperationException - if the add operation is not supported by this collectionClassCastException - if the class of the specified element prevents it from being added to this collectionNullPointerException - if the specified element is null and this collection does not permit null elementsIllegalArgumentException - if some property of the element prevents it from being added to this collectionIllegalStateException - if the element cannot be added at this time due to insertion restrictionsremoveboolean remove(Object o)Removes a single instance of the specified element from this collection, if it is present (optional operation). More formally, removes an element e such that (o==null ? e==null : o.equals(e)), if this collection contains one or more such elements. Returns true if this collection contained the specified element (or equivalently, if this collection changed as a result of the call).Parameters:o - element to be removed from this collection, if presentReturns:true if an element was removed as a result of this callThrows:ClassCastException - if the type of the specified element is incompatible with this collection (optional)NullPointerException - if the specified element is null and this collection does not permit null elements (optional)UnsupportedOperationException - if the remove operation is not supported by this collectioncontainsAllboolean containsAll(Collection c)Returns true if this collection contains all of the elements in the specified collection.Parameters:c - collection to be checked for containment in this collectionReturns:true if this collection contains all of the elements in the specified collectionThrows:ClassCastException - if the types of one or more elements in the specified collection are incompatible with this collection (optional)NullPointerException - if the specified collection contains one or more null elements and this collection does not permit null elements (optional), or if the specified collection is null.See Also:contains(Object)addAllboolean addAll(Collection c)Removes all of this collection's elements that are also contained in the specified collection (optional operation). After this call returns, this collection will contain no elements in common with the specified collection.Parameters:c - collection containing elements to be removed from this collectionReturns:true if this collection changed as a result of the callThrows:UnsupportedOperationException - if the removeAll method is not supported by this collectionClassCastException - if the types of one or more elements in this collection are incompatible with the specified collection (optional)NullPointerException - if this collection contains one or more null elements and the specified collection does not support null elements (optional), or if the specified collection is nullSee Also:remove(Object), contains(Object)removeIfdefault boolean removeIf(Predicate
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