课程：实现自己的权限

This lesson demonstrates how to write a class that defines its own special permission. The basic components in this lesson include:

1. A sample game called ExampleGame.
2. A class called HighScore, which is used by ExampleGame to store a user's latest high score.
3. A class called HighScorePermission, which is used to protect access to the user's stored high score value.
4. A user's security policy file, which grants permission to ExampleGame to update his/her high score.

The basic scenario is as follows:

1. A user plays ExampleGame.
2. If the user reaches a new high score, ExampleGame uses the HighScore class to save this new value.
3. The HighScore class looks into the user's security policy to check if ExampleGame has permission to update the user's high score value.
4. If ExampleGame has permission to update the high score, then the HighScore class updates that value.

We describe the key points of each of the basic components and then show a sample run:

• ExampleGame
• HighScore 类
• HighScorePermission 类
• 示例策略文件
• 把它们放在一起