iOS 开发基础知识梳理

1. Objective-C 语言基础

1.1 基本语法

• 头文件 (.h) 和 实现文件 (.m)
• 方法声明与实现：

  @interface Person : NSObject
  - (void)sayHello;
  @end
  
  @implementation Person
  - (void)sayHello {
      NSLog(@"Hello, World!");
  }
  @end

1.2 关键字

• @interface / @implementation：类的声明与实现
• @property / @synthesize / @dynamic：属性声明、自动合成、动态合成
• self / super：指向自身、调用父类方法
• id / instancetype：通用对象类型，推荐 instancetype 作为返回值
• delegate / protocol：协议与代理模式

1.3 内存管理

• MRC（手动引用计数）
  • retain / release / autorelease
• ARC（自动引用计数）
  • strong / weak / assign / copy
• 循环引用问题（weak 修饰，解决 retain cycle）

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2. UIKit 和界面开发

2.1 UIView 与 UIViewController

• 视图控制器生命周期

  - (void)viewDidLoad;
  - (void)viewWillAppear:(BOOL)animated;
  - (void)viewDidAppear:(BOOL)animated;
  - (void)viewWillDisappear:(BOOL)animated;
  - (void)viewDidDisappear:(BOOL)animated;

• 手写 UI vs Storyboard

  • 代码方式

    UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(20, 50, 200, 40)];
    label.text = @"Hello";
    [self.view addSubview:label];

  • Storyboard / XIB（可视化拖拽，适合小团队开发）

2.2 事件响应

• target-action 机制

  [button addTarget:self action:@selector(buttonTapped) forControlEvents:UIControlEventTouchUpInside];

• 手势识别

  UITapGestureRecognizer *tap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(viewTapped)];
  [self.view addGestureRecognizer:tap];

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3. 网络通信

3.1 NSURLSession

• GET 请求

  NSURL *url = [NSURL URLWithString:@"https://api.github.com/lalaluya/data"];
  NSURLSessionDataTask *task = [[NSURLSession sharedSession] dataTaskWithURL:url completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
      if (data) {
          NSDictionary *json = [NSJSONSerialization JSONObjectWithData:data options:0 error:nil];
          NSLog(@"%@", json);
      }
  }];
  [task resume];

• POST 请求

  NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:[NSURL URLWithString:@"https://api.github.com/lalaluya/login"]];
  request.HTTPMethod = @"POST";
  request.HTTPBody = [@"username=admin&password=123456" dataUsingEncoding:NSUTF8StringEncoding];

3.2 JSON 解析

• NSJSONSerialization 解析 JSON：

  NSDictionary *json = [NSJSONSerialization JSONObjectWithData:data options:kNilOptions error:nil];

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4. 数据存储

4.1 NSUserDefaults（轻量级存储）

[[NSUserDefaults standardUserDefaults] setObject:@"John" forKey:@"username"];
NSString *name = [[NSUserDefaults standardUserDefaults] stringForKey:@"username"];

4.2 文件存储

NSString *path = [NSHomeDirectory() stringByAppendingPathComponent:@"Documents/test.txt"];
[@"Hello, World!" writeToFile:path atomically:YES encoding:NSUTF8StringEncoding error:nil];

4.3 CoreData

NSFetchRequest *fetchRequest = [NSFetchRequest fetchRequestWithEntityName:@"Person"];
NSArray *result = [context executeFetchRequest:fetchRequest error:nil];

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5. 调试与优化

5.1 Xcode 调试

• 使用断点（breakpoint）
• po 命令打印对象：

  (lldb) po self.view

5.2 Instruments 性能分析

• Leaks 监测内存泄漏
• Time Profiler 分析 CPU 性能
• Allocations 监测内存分配

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