[NSDictionary getObjects:andKeys:]的示例

Question

我找不到该方法的工作示例[NSDictionary getObjects:andKeys:].我能找到的唯一例子,没有编译.我提供了错误/警告,以防有人搜索它们.

我感到困惑的原因是因为NSDictionary上的大多数方法都返回了NSArray.但是,在文档中,它声明此方法的out变量作为C数组返回.

以下是您按照链接示例可能获得的错误消息/警告:

NSDictionary *myDictionary = ...;

id objects[]; // Error: Array size missing in 'objects'
id keys[]; // Error: Array size missing in 'keys'

[myDictionary getObjects:&objects andKeys:&keys];

for (int i = 0; i < count; i++) {
  id obj = objects[i];
  id key = keys[i];
}

.

NSDictionary *myDictionary = ...;

NSInteger count = [myDictionary count];
id objects[count];
id keys[count];
[myDictionary getObjects:&objects andKeys:&keys]; // Warning: Passing argument 1 of 'getObjects:andKeys:' from incompatible pointer type.

for (int i = 0; i < count; i++) {
  id obj = objects[i];
  id key = keys[i];
}

我将提供一个有效的解决方案作为这个问题的答案.

Answer 1

以下是使用此方法的正确方法:

NSDictionary *myDictionary = [NSDictionary dictionaryWithObjectsAndKeys:@"1", @"A", @"2", @"B", nil];

NSInteger count = [myDictionary count];
id objects[count];
id keys[count];
[myDictionary getObjects:objects andKeys:keys];

for (int i = 0; i < count; i++) {
  id obj = objects[i];
  id key = keys[i];
  NSLog(@"%@ -> %@", obj, key);
}

Answer 2

在ARC下,解决方案需要修改如下(__unsafe_unretained添加到数组定义中):

NSDictionary *myDictionary = [NSDictionary dictionaryWithObjectsAndKeys:@"1", @"A", @"2", @"B", nil];

NSInteger count = [myDictionary count];
id __unsafe_unretained objects[count];
id __unsafe_unretained keys[count];
[myDictionary getObjects:objects andKeys:keys];

for (int i = 0; i < count; i++) {
  id obj = objects[i];
  id key = keys[i];
  NSLog(@"%@ -> %@", obj, key);
}