字典的两种取值的区别 （objectForKey： 和 valueForKey ）

一般来说 key 可以是任意字符串组合，如果 key 不是以 @ 符号开头，这时候 valueForKey: 等同于 objectForKey:，如果是以 @ 开头，去掉 key 里的 @ 然后用剩下部分作为 key 执行 [super valueForKey:]。

比如：

NSDictionary *dict = [NSDictionary dictionaryWithObject:@"theValue"

                                                 forKey:@"theKey"];

NSString *value1 = [dict objectForKey:@"theKey"];

NSString *value2 = [dict valueForKey:@"theKey"];

 

这时候 value1 和 value2 是一样的结果。如果是这样一个 dict：

NSDictionary *dict = [NSDictionary dictionaryWithObject:@"theValue"

                                                 forKey:@"@theKey"];// 注意这个 key 是以 @ 开头

NSString *value1 = [dict objectForKey:@"@theKey"];

NSString *value2 = [dict valueForKey:@"@theKey"];

 

value1 可以正确取值，但是 value2 取值会直接 crash 掉，报错信息：

Terminating app due to uncaught exception ‘NSUnknownKeyException’, reason: ‘[<__NSCFDictionary 0x892fd80> valueForUndefinedKey:]: this class is not key value coding-compliant for the key theKey.’

这是因为 valueForKey: 是 KVC(NSKeyValueCoding) 的方法，在 KVC 里可以通过 property 同名字符串来获取对应的值。比如：

@interface Person : NSObject

@property (nonatomic, retain) NSString *name;

@end

...

Person *person = [[Person alloc] init];

person.name = @"fannheyward";

NSLog(@"name:%@", [person name]);

//name:fannheyward

NSLog(@"name:%@", [person valueForKey:@"name"]);

//name:fannheyward

[person release];

 

valueForKey: 取值是找和指定 key 同名的 property accessor，没有的时候执行 valueForUndefinedKey:，而 valueForUndefinedKey: 的默认实现是抛出 NSUndefinedKeyException 异常。

回过头来看刚才 crash 的例子， [dict valueForKey:@"@theKey"]; 会把 key 里的 @ 去掉，也就变成了 [dict valueForKey:@"theKey"];，而 dict 不存在 theKey 这样的 property，转而执行 [dict valueForUndefinedKey:@"theKey"];，抛出 NSUndefinedKeyException 异常后 crash 掉。

objectForKey: 和 valueForKey: 在多数情况下都是一样的结果返回，但是如果 key 是以 @ 开头，valueForKey: 就成了一个大坑，建议在 NSDictionary 下只用 objectForKey: 来取值。

 

修改导航栏的背景颜色：

修改tableView 的右侧的索引的颜色：

 更改索引的背景颜色:

self.tableView.sectionIndexBackgroundColor = [UIColor clearColor];

更改索引的文字颜色:

self.tableView.sectionIndexColor = [UIColor blueColor];

tableview 的系统自带的编辑按钮的修改

 

////  RootViewController.m//  13////  Created by lanounjw on 15/9/13.//  Copyright (c) 2015年 lanouhn. All rights reserved.//#import "RootViewController.h"#import "Contacts.h"#import "ContactCell.h"#import "UIImage+Scale.h"#import "macroHeader.h"@interface RootViewController ()
      
       @property(nonatomic,retain)NSMutableDictionary * dataDic;@property(nonatomic,retain)NSMutableArray * sortedKey;@property(nonatomic,retain)Contacts * per;@end@implementation RootViewController- (void)viewDidLoad {    [super viewDidLoad];    [self customerNavBar];    [self readFromLoca];    //创建 tableView    UITableView * tableview = [[UITableView alloc]initWithFrame:[[UIScreen mainScreen]bounds] style:UITableViewStylePlain];    tableview.separatorColor = [UIColor grayColor];    tableview.separatorInset = UIEdgeInsetsMake(0, 10, 0, 10);    tableview.dataSource = self;    tableview.delegate = self;    //更改索引的背景颜色:    tableview.sectionIndexBackgroundColor = [UIColor clearColor];    //更改索引的文字颜色:    tableview.sectionIndexColor = UIColorFromHex(0x66CDAA);    self.view = tableview;    [tableview release];}-(void)customerNavBar{    self.navigationItem.title = @"zzs150739";    UIBarButtonItem * left = [[UIBarButtonItem alloc]initWithImage:[[UIImage imageNamed:@"add_contact@2x"] imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal] style:UIBarButtonItemStylePlain target:self action:@selector(handleNewContact:)];    self.navigationItem.leftBarButtonItem = left;    [left release];    self.navigationController.navigationBar.barTintColor = UIColorFromHex(0x66CDAA);#pragma mark---添加自带的编辑按钮    self.editButtonItem.title = @"编辑";    self.navigationItem.rightBarButtonItem = self.editButtonItem;    self.editButtonItem.tintColor = [UIColor whiteColor];}#pragma mark---添加自带的编辑按钮后重写编辑的方法-(void)setEditing:(BOOL)editing animated:(BOOL)animated{    [super setEditing:editing animated:animated];    [(UITableView *)self.view setEditing:editing animated:YES];    if (self.editing) {        self.editButtonItem.title = @"完成";    }else{        self.editButtonItem.title = @"修改";    }}#pragma mark---设置某些区域可以被修改-(BOOL)tableView:(UITableView *)tableView canEditRowAtIndexPath:(NSIndexPath *)indexPath{    if (indexPath.row == 0) {        return YES;//NO 就是不能被修改    }    return YES;}#pragma mark---提交编辑状态//处理数据以及页面(真正的数据是放在字典或者集合里)-(void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath{    NSString * key = [self.sortedKey objectAtIndex:indexPath.section];    NSMutableArray * group = [_dataDic objectForKey:key];    Contacts * contact = [group objectAtIndex:indexPath.row];    if (editingStyle == UITableViewCellEditingStyleDelete) {        if ([group count] == 1) {            [_dataDic removeObjectForKey:key];            [_sortedKey removeObject:key];            [tableView deleteSections:[NSIndexSet indexSetWithIndex:indexPath.section] withRowAnimation:UITableViewRowAnimationBottom];        }else{            [group removeObject:contact];            [tableView deleteRowsAtIndexPaths:@[indexPath] withRowAnimation:UITableViewRowAnimationLeft];        }    }else{        NSDictionary * dic = @{
    @"name":@"白白",@"gender":@"男",@"phoneNum":@"13523526303",@"photo":@"oooo"};        Contacts * newPer = [[Contacts alloc]initWithDic:dic];        [group  insertObject:newPer atIndex:indexPath.row];        [tableView insertRowsAtIndexPaths:@[indexPath] withRowAnimation:UITableViewRowAnimationRight];        [newPer release];    }}#pragma mark---tableView 的 cell 的移动-(BOOL)tableView:(UITableView *)tableView canMoveRowAtIndexPath:(NSIndexPath *)indexPath{    return YES;}#pragma mark---提交移动后的结果-(void)tableView:(UITableView *)tableView moveRowAtIndexPath:(NSIndexPath *)sourceIndexPath toIndexPath:(NSIndexPath *)destinationIndexPath{    NSString * key = [self.sortedKey objectAtIndex:sourceIndexPath.section];    NSMutableArray * group = [self.dataDic objectForKey:key];    Contacts * per = [[group objectAtIndex:sourceIndexPath.row]retain];    [group removeObjectAtIndex:sourceIndexPath.row];    [group insertObject:per atIndex:destinationIndexPath.row];    [per release];}#pragma mark---限定 cell 的移动界限，禁止跨区运动-(NSIndexPath *)tableView:(UITableView *)tableView targetIndexPathForMoveFromRowAtIndexPath:(NSIndexPath *)sourceIndexPath toProposedIndexPath:(NSIndexPath *)proposedDestinationIndexPath{    if (sourceIndexPath.section == proposedDestinationIndexPath.section) {        return proposedDestinationIndexPath;    }else{        return sourceIndexPath;    }}#pragma mark---修改删除按钮的文字-(NSString *)tableView:(UITableView *)tableView titleForDeleteConfirmationButtonForRowAtIndexPath:(NSIndexPath *)indexPath{    return @"删除";}#pragma mark---tableview的 cell 的编辑样式-(UITableViewCellEditingStyle)tableView:(UITableView *)tableView editingStyleForRowAtIndexPath:(NSIndexPath *)indexPath{    if (indexPath.section == 0) {        return UITableViewCellEditingStyleInsert;    }    return UITableViewCellEditingStyleDelete;}#pragma mark---#pragma mark---添加联系人页面-(void)handleNewContact:(UIBarButtonItem *)sender{    //添加联系人}#pragma mark---读取本地数据-(void)readFromLoca{    NSString * filePath = [[NSBundle mainBundle]pathForResource:@"contacts" ofType:@"plist"];    self.dataDic = [NSMutableDictionary dictionaryWithContentsOfFile:filePath];    NSDictionary * dic = [NSDictionary dictionaryWithDictionary:_dataDic];    NSArray * sorted = [[dic allKeys]sortedArrayUsingSelector:@selector(compare:)];    self.sortedKey = [NSMutableArray arrayWithArray:sorted];    for (NSString * key in self.sortedKey) {        NSMutableArray * contactArr = [NSMutableArray array];        NSArray * group = [NSArray arrayWithArray:[_dataDic objectForKey:key]];        for (NSDictionary * dic in group) {            Contacts * per = [[Contacts alloc]initWithDic:dic];            [contactArr addObject:per];        }        [self.dataDic setObject:contactArr forKey:key];    }}#pragma mark ---2个必须实现的方法-(NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section{    return [[self.dataDic objectForKey:self.sortedKey[section]] count];}-(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath{    static NSString  * identifier = @"cell";   ContactCell *cell = [tableView dequeueReusableCellWithIdentifier:identifier];    if (!cell) {        cell = [[ContactCell alloc]initWithStyle:UITableViewCellStyleValue1 reuseIdentifier:identifier];    }    NSString * key = [self.sortedKey objectAtIndex:indexPath.section];    NSArray * group = [self.dataDic objectForKey:key];    Contacts * contact = [group objectAtIndex:indexPath.row];    self.per = contact;    cell.nameLabel.text = _per.name;    cell.photoView.image = [[UIImage imageNamed:_per.photo] setScaleTOSize:CGSizeMake(50, 50)];    cell.contentLabel.text = _per.phoneNum;    return cell;}#pragma mark---右侧索引-(NSArray *)sectionIndexTitlesForTableView:(UITableView *)tableView{    NSArray * arr = [[self.dataDic allKeys]sortedArrayUsingSelector:@selector(compare:)];    return arr;}#pragma mark---标题页面-(NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section{    NSString * titleName = self.sortedKey[section];    return titleName;}#pragma mark---页眉行高-(CGFloat)tableView:(UITableView *)tableView heightForHeaderInSection:(NSInteger)section{    return 40;}#pragma mark---cell行高-(CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath{    return 90;}#pragma mark---分区数目-(NSInteger)numberOfSectionsInTableView:(UITableView *)tableView{    return [[self.dataDic allKeys] count];}#pragma mark---内存警告- (void)didReceiveMemoryWarning {    [super didReceiveMemoryWarning];    if ([self isViewLoaded] && !self.view.window) {        self.view = nil;    }}@end