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[8.x] Add Collection@isSingle method #36428

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Merged
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Mar 2, 2021
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[8.x] Add Collection@isSingle method #36428

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10 changes: 10 additions & 0 deletions src/Illuminate/Collections/Collection.php
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Original file line number Diff line number Diff line change
Expand Up @@ -553,6 +553,16 @@ public function isEmpty()
return empty($this->items);
}

/**
* Determine if the collection contains a single element.
*
* @return bool
*/
public function isSingle()
{
return $this->count() === 1;
}

/**
* Join all items from the collection using a string. The final items can use a separate glue string.
*
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10 changes: 10 additions & 0 deletions src/Illuminate/Collections/LazyCollection.php
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Expand Up @@ -556,6 +556,16 @@ public function isEmpty()
return ! $this->getIterator()->valid();
}

/**
* Determine if the collection contains a single element.
*
* @return bool
*/
public function isSingle()
{
return $this->take(2)->count() === 1;
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@gocanto gocanto Mar 2, 2021

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why is take(2) necessary? :)

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@JosephSilber JosephSilber Mar 2, 2021 •
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@gocanto without it, the whole collection would have to be enumerated, which is a waste.

As soon as we know that there are 2, we know that it's not single!

See this test, which ensures we don't enumerate more than 2 items:

framework/tests/Support/SupportLazyCollectionIsLazyTest.php

Lines 487 to 492 in b72178d

public function testIsSingleIsLazy()
{
$this->assertEnumerates(2, function ($collection) {
$collection->isSingle();
});
}

Without take(2), this test would fail.

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@gocanto gocanto Mar 2, 2021

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cool stuff.

}

/**
* Join all items from the collection using a string. The final items can use a separate glue string.
*
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10 changes: 10 additions & 0 deletions tests/Support/SupportCollectionTest.php
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Expand Up @@ -541,6 +541,16 @@ public function testCountableByWithCallback($collection)
})->all());
}

/**
* @dataProvider collectionClassProvider
*/
public function testIsSingle($collection)
{
$this->assertFalse((new $collection([]))->isSingle());
$this->assertTrue((new $collection([1]))->isSingle());
$this->assertFalse((new $collection([1, 2]))->isSingle());
}

public function testIterable()
{
$c = new Collection(['foo']);
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7 changes: 7 additions & 0 deletions tests/Support/SupportLazyCollectionIsLazyTest.php
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Expand Up @@ -484,6 +484,13 @@ public function testIsNotEmptyIsLazy()
});
}

public function testIsSingleIsLazy()
{
$this->assertEnumerates(2, function ($collection) {
$collection->isSingle();
});
}

public function testJoinIsLazy()
{
$this->assertEnumeratesOnce(function ($collection) {
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