objective-c 以最节省内存的方式循环自定义对象的 NSMutableArray
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Loop through NSMutableArray of custom objects in the most memory efficient way
提问by James P. Wright
What is the most memory efficient way to loop through an NSMutableArray of custom objects? I need to check a value in each object in the array and return how many of that type of object is in the array.
循环遍历自定义对象的 NSMutableArray 的最有效内存方法是什么？我需要检查数组中每个对象的值并返回数组中该类型对象的数量。
回答by refulgentis
for (WhateverYourClassNameIs *whateverNameYouWant in yourArrayName) {
[whateverNameYouWant performSelector];
more code here;
}
It's called fast enumeration and was a new feature with Objective C 2.0, which is available on the iPhone.
它被称为快速枚举，是 Objective C 2.0 的一项新功能，可在 iPhone 上使用。
回答by Dave DeLong
I'd probably just use a predicate, which would be something like this:
我可能只是使用一个谓词，这将是这样的：
NSArray * filtered = [myArray filteredArrayUsingPredicate:[NSPredicate predicateWithFormat:@"aProperty = %@", @"someValue"]];
NSLog(@"number of items where aProperty = someValue: %d", [filtered count]);
Edit: This code is functionally equivalent to:
编辑：此代码在功能上等效于：
NSMutableArray * filtered = [NSMutableArray array];
for (MyCustomObject * object in myArray) {
if ([[object aProperty] isEqual:@"someValue"]) {
[filtered addObject:object];
}
}
