基础类型

发表于 2015-09-09 更新于 2026-06-10 分类于移动开发

NSArray

##排序

逆序，array.reverseObjectEnumerator.allObjects
数组中是字符串对象排序首选sortedArrayUsingSelector:

NSArray *array = @[@”John Appleseed”, @”Tim Cook”, @”Hair Force One”, @”Michael Jurewitz”];

NSArray *sortedArray = [array sortedArrayUsingSelector:@selector(localizedCaseInsensitiveCompare:)];

存储内容是数字

NSArray *numbers = @[@9, @5, @11, @3, @1];

NSArray *sortedNumbers = [numbers sortedArrayUsingSelector:@selector(compare:)];
使用函数指针sortedArrayHint排序
- (NSData *)sortedArrayHint;
- (NSArray )sortedArrayUsingFunction:(NSInteger ()(id, id, void *))comparator
  
  context:(void *)context;
- (NSArray )sortedArrayUsingFunction:(NSInteger ()(id, id, void *))comparator
  
  context:(void *)context hint:(NSData *)hint;
基于block的排序方法
- (NSArray *)sortedArrayUsingComparator:(NSComparator)cmptr;
- (NSArray *)sortedArrayWithOptions:(NSSortOptions)opts
  
  usingComparator:(NSComparator)cmptr;
性能比较selector最快

Sorting 1000000 elements. selector: 4947.90[ms] function: 5618.93[ms] block: 5082.98[ms].
更快的二分查找

typedef NS_OPTIONS(NSUInteger, NSBinarySearchingOptions) {
```
 NSBinarySearchingFirstEqual = (1UL << 8),

 NSBinarySearchingLastEqual = (1UL << 9),

 NSBinarySearchingInsertionIndex = (1UL << 10),
```
};
- (NSUInteger)indexOfObject:(id)obj
  
  inSortedRange:(NSRange)r
  
  options:(NSBinarySearchingOptions)opts
  
  usingComparator:(NSComparator)cmp;
//Time to search for 1000 entries within 1000000 objects. Linear: 54130.38[ms]. Binary: 7.62[ms]

枚举

使用indexesOfObjectsWithOptions:passingTest:

NSIndexSet *indexes = [randomArray indexesOfObjectsWithOptions:NSEnumerationConcurrent
```
 passingTest:^BOOL(id obj, NSUInteger idx, BOOL *stop) {

 return testObj(obj);
```
}];

NSArray *filteredArray = [randomArray objectsAtIndexes:indexes];
传统的枚举

NSMutableArray *mutableArray = [NSMutableArray array];

for (id obj in randomArray) {
```
 if (testObj(obj)) {

      [mutableArray addObject:obj];

 }
```
}
block方式枚举

NSMutableArray *mutableArray = [NSMutableArray array];

[randomArray enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
```
 if (testObj(obj)) {

      [mutableArray addObject:obj];

 }
```
}];
通过下标objectAtIndex:

NSMutableArray *mutableArray = [NSMutableArray array];

for (NSUInteger idx = 0; idx < randomArray.count; idx++) {
```
 id obj = randomArray[idx];

 if (testObj(obj)) {

      [mutableArray addObject:obj];

 }
```
}
使用比较传统的学院派NSEnumerator

NSMutableArray *mutableArray = [NSMutableArray array];

NSEnumerator *enumerator = [randomArray objectEnumerator];

id obj = nil;

while ((obj = [enumerator nextObject]) != nil) {
```
 if (testObj(obj)) {

      [mutableArray addObject:obj];

 }
```
}
使用predicate

NSArray *filteredArray2 = [randomArray filteredArrayUsingPredicate:[NSPredicate predicateWithBlock:^BOOL(id obj, NSDictionary *bindings) {
```
 return testObj(obj);
```
}]];
各个方法枚举时间参考，indexesOfObjectsWithOptions在开启了并发枚举的情况下比NSFastEnumeration快一倍。

枚举方法 / 时间 [ms]	10.000.000 elements	10.000 elements
indexesOfObjects:, concurrent	1844.73	2.25
NSFastEnumeration (for in)	3223.45	3.21
indexesOfObjects:	4221.23	3.36
enumerateObjectsUsingBlock:	5459.43	5.43
objectAtIndex:	5282.67	5.53
NSEnumerator	5566.92	5.75
filteredArrayUsingPredicate:	6466.95	6.31

NSDictionary

性能

同样数目的值，NSDictionary比NSArray要花费多得多的内存空间

排序

使用NSArray的排序方法将键数组排序为新的对象

- (NSArray *)keysSortedByValueUsingSelector:(SEL)comparator;

- (NSArray *)keysSortedByValueUsingComparator:(NSComparator)cmptr;

- (NSArray *)keysSortedByValueWithOptions:(NSSortOptions)opts

     usingComparator:(NSComparator)cmptr;

枚举

keysOfEntriesWithOptions:passingTest:，可并行

NSSet *matchingKeys = [randomDict keysOfEntriesWithOptions:NSEnumerationConcurrent

passingTest:^BOOL(id key, id obj, BOOL *stop)

{
```
 return testObj(obj);
```
}];

NSArray *keys = matchingKeys.allObjects;

NSArray *values = [randomDict objectsForKeys:keys notFoundMarker:NSNull.null];

__unused NSDictionary *filteredDictionary = [NSDictionary dictionaryWithObjects:values
```
 forKeys:keys];
```
getObjects:andKeys: 枚举，基于c数组

NSMutableDictionary *mutableDictionary = [NSMutableDictionary dictionary];

id __unsafe_unretained objects[numberOfEntries];

id __unsafe_unretained keys[numberOfEntries];

[randomDict getObjects:objects andKeys:keys];

for (int i = 0; i < numberOfEntries; i++) {
```
 id obj = objects[I];

 id key = keys[I];

 if (testObj(obj)) {

      mutableDictionary[key] = obj;

 }
```
}
block枚举

NSMutableDictionary *mutableDictionary = [NSMutableDictionary dictionary];

[randomDict enumerateKeysAndObjectsUsingBlock:^(id key, id obj, BOOL *stop) {
```
 if (testObj(obj)) {

      mutableDictionary[key] = obj;

 }
```
}];
NSFastEnumeration

NSMutableDictionary *mutableDictionary = [NSMutableDictionary dictionary];

for (id key in randomDict) {
```
 id obj = randomDict[key];

 if (testObj(obj)) {

      mutableDictionary[key] = obj;

 }
```
}
NSEnumeration

NSMutableDictionary *mutableDictionary = [NSMutableDictionary dictionary];

NSEnumerator *enumerator = [randomDict keyEnumerator];

id key = nil;

while ((key = [enumerator nextObject]) != nil) {
```
 id obj = randomDict[key];

 if (testObj(obj)) {

      mutableDictionary[key] = obj;

 }
```
}
各个方法枚举时间参考

枚举方法 / 时间 [ms]	50.000 elements	1.000.000 elements
keysOfEntriesWithOptions:, concurrent	16.65	425.24
getObjects:andKeys:	30.33	798.49
keysOfEntriesWithOptions:	30.59	856.93
enumerateKeysAndObjectsUsingBlock:	36.33	882.93
NSFastEnumeration	41.20	1043.42
NSEnumeration	42.21	1113.08