Might not be a question specific to Eloquent collections, but it just hit me while working with them. Let's just assume we have a $collection object which is an instance of Illuminate\Support\Collection.
Now if we want to iterate over it, what are the pros and cons of using each() with a closure versus a regular foreach. Are there any?
foreach ($collection as $item) {
// Some code
}
versus
$collection->each(function ($item) {
// Some code
});
A foreach statement should be used as a sort of a way to cycle through a collection and perform some sort of logic on it. If what is in it effects other things in the program, then use this loop.
The .each method uses array_map to cycle through each of the objects in the collection and perform a closure on each one. It then returns the resulting array. That is the key! .each should be used if you want to change the collection in some way. Maybe it's an array of cars and you want to make the model upper case or lower case. You would just pass a closure to the .each method that takes the object and calls strtoupper() on the model of each Car object. It then returns the collection with the changes that have been made.
故事的寓意是:使用.each方法以某种方式更改数组中的每个项目；使用foreach循环使用每个对象影响程序的其他部分(使用一些逻辑语句).
如此Eloquent 地陈述(看到我在那里做了什么吗？)下面，上述答案略有偏差.使用array_map的.each方法实际上从未使用过array_map调用的输出.因此，array_map创建的新数组不会保存在Collection上.要更改它，最好使用.map方法，该方法也存在于Collection对象上.
使用foreach语句对它们进行迭代更有意义，因为除非确保使用use语句，否则将无法访问闭包之外的变量，这在我看来很尴尬.
最初编写上述答案时的实现可以是found here.
.each in Laravel 5.1The new .each that they are talking about below no longer uses array_map. It simply iterates through each item in the collection and calls the passed in $callback, passing it the item and its key in the array. Functionally, it seems to work the same. I believe using a foreach loop would make more sense when reading the code. However, I see the benefits of using .each because it allows you to chain methods together if that tickles your fancy. It also allows you to return false from the callback to leave the loop early if your business logic demands you to be able to.
有关新实现的更多信息，请查看the source code.