1224 Dictionary Dictionary

Immutable dictionary Nsdictionary

Dictionaries have no order, key-value pairs

Key-value

Key (String object)-Value (object)

0. The values of multiple key-value pairs can be the same in a dictionary, but the keys cannot be the same and must be unique

1. Advantages of dictionary Storage

A. Easy to find

B. Easy to hack

2. How to create a dictionary

Nsdictionary *dic = @{@ "Xiao Wang": xw,@ "Zhang San": zs,@ "ls": ls};

Nsdictionary *dic1 = [Nsdictionary dictionary];

Nsdictionary *dic1_ = [[Nsdictionary alloc]init];

Nsdictionary *dic2 = [Nsdictionary dictionarywithdictionary:dic];

Nsdictionary *dic2_ = [[Nsdictionary alloc]initwithdictionary:dic];

Initializes a key-value pair

Nsdictionary *dic3 = [nsdictionary dictionarywithobject:xw forkey:@ "Xiao Wang"];

Create a dictionary with multiple key-value pairs

Nsdictionary *dic4 = [nsdictionary Dictionarywithobjects:@[xw,zs,ls] forkeys:@[@ "Xiaowang", @ "Zhangsan", @ "Lisi"];

3. Get the number of dictionary key-value pairs

NSLog (@ "Count:%ld", Dic5.count);

4, get all keys keys (String object)

Nsarray*allkeys = [Dic5 AllKeys];

5, get all the value

Nsarray *allvalues = [Dic5 allvalue];

6. Traverse a dictionary

For (NSString *key in AllKeys) {

NSLog (@ "key =%@:value =%@", key,[dic5 Objectforkey:key]);

}

7, get the corresponding value by key

Nsarray *temparray = [dic5 objectforkey:@ "Man"]);

Nsmubtabledictionary

1. Creating a mutable Dictionary

Nsmutabledictionary *mdic = [Nsmutabledictionary dictionarywithcapacity:0];

2. Add a key-value pair

[MDic setobject:@ "YQL" forkey:@ "name"];

[MDic setobject:parray forkey:@ "man"];

[MDic setobject:@ "Red Mansions" forkey:@ "classics"];

NSLog (@ "7.%@", mDic);

3. Change the value of a key

[MDic setobject:@ "Hongloumeng" forkey:@ "classics"];

4. Delete key-value pairs

[MDic removeobjectsforkeys:@ "Classics"];

[MDic removeobjectsforkeys:@[@ "man", @ "NB", @ "Hel"];

[MDic removeallobjects];

NSLog (@ "8..%@", mDic);

1224 Dictionary Dictionary