NSDictionary翻译过来叫做”字典”
日常生活中,“字典”的作用:通过一个拼音或者汉字,就能找到对应的详细解释
NSDictionary的作用类似:通过一个key,就能找到对应的value
NSDictionary是不可变的, 一旦初始化完毕, 里面的内容就无法修改
2.NSDictionary的创建
+ (instancetype)dictionary;
+ (instancetype)dictionaryWithObject:(id)object forKey:(id <NSCopying>)key;
+ (instancetype)dictionaryWithObjectsAndKeys:(id)firstObject, ...;
+ (id)dictionaryWithContentsOfFile:(NSString *)path;
+ (id)dictionaryWithContentsOfURL:(NSURL *)url;
NSDictionary创建简写
以前NSDictionary *dict = [NSDictionary dictionaryWithObjectsAndKeys:@"lnj", @"name", @"12345678", @"phone", @"天朝", @"address", nil];
现在NSDictionary *dict = @{@"name":@"lnj", @"phone":@"12345678", @"address":@"天朝"};
NSDictionary *dict = @{@"name":@"lnj", @"phone":@"12345678", @"address":@"天朝"};
for (NSString *key in dict) {
NSLog(@"key = %@, value = %@", key, dict[key]);
Block遍历
[dict enumerateKeysAndObjectsUsingBlock:^(NSString *key, NSString *obj, BOOL *stop) {
NSLog(@"key = %@, value = %@", key, obj);
4.NSDictionary文件操作
将字典写入文件中
- (BOOL)writeToFile:(NSString *)path atomically:(BOOL)useAuxiliaryFile;
- (BOOL)writeToURL:(NSURL *)url atomically:(BOOL)atomically;
存结果是xml文件格式,但苹果官方推荐为plist后缀。
NSDictionary *dict = @{@"name":@"lnj", @"phone":@"12345678", @"address":@"天朝"};
BOOL flag = [dict writeToFile:@"/Users/LNJ/Desktop/dict.plist" atomically:YES];
NSLog(@"flag = %i", flag);
从文件中读取字典
NSDictionary *newDict = [NSDictionary dictionaryWithContentsOfFile:@"/Users/LNJ/Desktop/dict.plist"];
NSLog(@"newDict = %@", newDict);
