NSDictionary 按浮点数形式对键进行排序

使用NSDictionary对键进行排序是iOS开发中常见的需求之一。NSDictionary是一种无序的键值对集合，如果我们希望按照键的某种顺序来访问其中的元素，就需要对键进行排序。而对于键为浮点数的情况，我们可以使用NSNumber类型来表示浮点数键，并通过比较NSNumber对象的值来实现排序。

objective-c
// 创建一个包含浮点数键的NSDictionary对象
NSDictionary *dict = @{@3.14: @"圆周率", @2.718: @"自然常数", @1.414: @"根号2"};
// 获取字典中所有键，并进行排序
NSArray *sortedKeys = [[dict allKeys] sortedArrayUsingSelector:@selector(compare:)];
// 遍历排序后的键数组，并输出对应的值
for (NSNumber *key in sortedKeys) {
    NSLog(@"键：%@，值：%@", key, dict[key]);
}

objective-c
NSDictionary *dict = @{@"c": @"C", @"a": @"A", @"b": @"B"};
NSArray *sortedKeys = [[dict allKeys] sortedArrayUsingSelector:@selector(compare:)];
for (NSString *key in sortedKeys) {
    NSLog(@"键：%@，值：%@", key, dict[key]);
}

objective-c
NSDictionary *dict = @{@"apple": @5, @"banana": @2, @"orange": @3};
NSArray *sortedKeys = [[dict allKeys] sortedArrayUsingComparator:^NSComparisonResult(id obj1, id obj2) {
    NSNumber *value1 = dict[obj1];
    NSNumber *value2 = dict[obj2];
    return [value2 compare:value1]; // 降序排序
}];
for (NSString *key in sortedKeys) {
    NSLog(@"键：%@，值：%@", key, dict[key]);
}

objective-c
NSDictionary *dict = @{@"apple": @5, @"banana": @2, @"orange": @3};
NSArray *sortedKeys = [[dict allKeys] sortedArrayUsingComparator:^NSComparisonResult(id obj1, id obj2) {
    NSString *key1 = obj1;
    NSString *key2 = obj2;
    return [@([key1 length]) compare:@([key2 length])]; // 升序排序
}];
for (NSString *key in sortedKeys) {
    NSLog(@"键：%@，值：%@", key, dict[key]);
}