利用多核优势，遍历NSDictionary

在现在多核CPU的时代，如果遍历NSDictionary的时候你还是通过先取key，在通过key取v alue的方式，你就out啦

NSMutableDictionary        *_dbalertlogMap;
[_dbalertlogMap enumerateKeysAndObjectsUsingBlock:^(id key, id obj,   BOOL *stop) {
NSLog(@“value for key %@ is %@”, key, value);
}

用这种办法可以充分利用CPU性能。

下面再把传统的几个遍历方式总结下：

方法一：

- (void)describeDictionary:(NSDictionary *dict)
{
NSArray *keys;
int i, count;
id key, value;
keys = [dict allKeys];
count = [keys count];
for (i = 0; i < count; i++)
{
key = [keys objectAtIndex: i];
value = [dict objectForKey: key];
NSLog (@"Key: %@ for value: %@", key, value);
}
}

方法二：

NSDictionary *dict = [NSDictionary dictionaryWithObjectsAndKeys:@"value1", @"key1", @"value2", @"key2", nil];

for (NSString *key in dict) {
NSLog(@"key: %@ value: %@", key, dict[key]);
}

方法三

NSLog(@"Hello, World!");
NSDictionary *myDic=[[NSDictionary alloc]initWithObjectsAndKeys:@"张三",@"name",@"李四",@"name", nil];

NSUInteger count = [myDic count];
NSLog(@"词典的数量为：  %lu",count);

NSEnumerator * myEnumerator = [myDic keyEnumerator];

for (NSObject *object in myEnumerator) {
NSLog(@"遍历KEY的值: %@",object);
}

myEnumerator = [[myDic allValues] objectEnumerator];
NSString *value;
while((value = [myEnumerator nextObject]))
{
NSLog(@"遍历的值: %@",value);
}

//通过KEY找到value
NSObject *myObject = [myDic objectForKey:@"name"];

if (myObject != nil) {
NSLog(@"通过KEY找到的value是: %@",myObject);
}

NSMutableDictionary *mydic2 = [NSMutableDictionary dictionaryWithCapacity:10];
[mydic2 setObject:@"Alex Hu" forKey:@"name"];
[mydic2 setObject:@"1388888888" forKey:@"mobile number"];

for (NSObject *object in [mydic2 objectEnumerator]) {
NSLog(@"遍历的值: %@",object);
}