IOS SDK详解之NSDictionary

转载：blog.csdn.net/hello_hwc

前言：本文将要讲述的内容有

1.NSDictionary 以及 NSMutableDictionary 概述

2.常用属性方法举例（不常用的本文不会涉及）

一 NSDictionary/NSMutableDictionary概述

NSDictionary提供了一种key－value的数据存储方式。总的来说，任何对象都可以作为key，只要其遵循NSCopying协议。其中，key不能相同（由isEqual来判断）。key和value都不能为nil，如果要表达一个空的值，用NSNull。NSDictionary中的值不可变。

NSMutableDictionary是NSDictionary的子类，是可变的字典。

二 NSDictionary常用的属性方法举例

2.1 创建和初始化

创建兼初始化

<code class=" hljs css">(<span class="hljs-tag">instancetype</span>)<span class="hljs-tag">dictionaryWithContentsOfFile</span><span class="hljs-pseudo">:(NSString</span> *)<span class="hljs-tag">path</span>
(<span class="hljs-tag">instancetype</span>)<span class="hljs-tag">dictionary</span>;
(<span class="hljs-tag">instancetype</span>)<span class="hljs-tag">dictionaryWithDictionary</span><span class="hljs-pseudo">:(NSDictionary</span> *)
(<span class="hljs-tag">instancetype</span>)<span class="hljs-tag">dictionaryWithObjects</span><span class="hljs-pseudo">:(NSArray</span> *)<span class="hljs-tag">objects</span>   <span class="hljs-tag">forKeys</span><span class="hljs-pseudo">:(NSArray</span> *)<span class="hljs-tag">keys</span>
(<span class="hljs-tag">instancetype</span>)<span class="hljs-tag">dictionaryWithObjectsAndKeys</span><span class="hljs-pseudo">:(id)firstObject</span></code>

初始化

<code class=" hljs erlang">-<span class="hljs-params">(<span class="hljs-variable">NSDictionary</span> *)</span>init;
-<span class="hljs-params">(<span class="hljs-variable">NSDictionary</span> *)</span>initWithContentsOfFile:<span class="hljs-params">(<span class="hljs-variable">NSString</span> *)</span>path;
-<span class="hljs-params">(<span class="hljs-variable">NSDictionary</span> *)</span>initWithDictionary:<span class="hljs-params">(<span class="hljs-variable">NSDictionary</span> *)</span>;
-<span class="hljs-params">(<span class="hljs-variable">NSDictionary</span> *)</span>initWithObjects:<span class="hljs-params">(<span class="hljs-variable">NSArray</span> *)</span>objects   forKeys:<span class="hljs-params">(<span class="hljs-variable">NSArray</span> *)</span>keys;
-<span class="hljs-params">(<span class="hljs-variable">NSDictionary</span> *)</span>initWithObjectsAndKeys:<span class="hljs-params">(id)</span>firstObject;</code>

就个人而言，我比较习惯后一种。当然，快捷创建的方式不要忘记了

符号

@{}

举例：

<code class=" hljs objectivec">    <span class="hljs-built_in">NSDictionary</span> * emptyDic = [<span class="hljs-built_in">NSDictionary</span> dictionary];
<span class="hljs-built_in">NSDictionary</span> * firstDic = @{@<span class="hljs-string">"key"</span>:@<span class="hljs-string">"value"</span>,
@<span class="hljs-string">"first"</span>:@<span class="hljs-string">"1"</span>};
<span class="hljs-built_in">NSDictionary</span> * secondDic = [[<span class="hljs-built_in">NSDictionary</span> alloc] initWithObjectsAndKeys:@<span class="hljs-string">"value1"</span>,@<span class="hljs-string">"key1"</span>,@<span class="hljs-string">"value2"</span>,@<span class="hljs-string">"key2"</span>,<span class="hljs-literal">nil</span>];</code>

2.2 count

返回key－value对的个数

<code class=" hljs objectivec">    <span class="hljs-built_in">NSDictionary</span> * dic = @{@<span class="hljs-string">"key1"</span>:@<span class="hljs-string">"1"</span>,
@<span class="hljs-string">"key2"</span>:@<span class="hljs-string">"2"</span>};
<span class="hljs-built_in">NSLog</span>(@<span class="hljs-string">"%d"</span>,dic<span class="hljs-variable">.count</span>);</code>

2.3 isEqualToDictionary比较两个dictionary内容是否一样。

<code class=" hljs objectivec">    <span class="hljs-built_in">NSDictionary</span> * dic1 = @{@<span class="hljs-string">"key1"</span>:@<span class="hljs-string">"1"</span>,
@<span class="hljs-string">"key2"</span>:@<span class="hljs-string">"2"</span>};
<span class="hljs-built_in">NSDictionary</span> * dic2 = @{@<span class="hljs-string">"key2"</span>:@<span class="hljs-string">"2"</span>,
@<span class="hljs-string">"key1"</span>:@<span class="hljs-string">"1"</span>};
<span class="hljs-keyword">if</span> ([dic1 isEqualToDictionary:dic2]) {
<span class="hljs-built_in">NSLog</span>(@<span class="hljs-string">"Equal contents"</span>);
}</code>

2.4 objectForKey: 和valueForKey 由属性获得内容

<code class=" hljs objectivec">    <span class="hljs-built_in">NSDictionary</span> * dic1 = @{@<span class="hljs-string">"key1"</span>:@<span class="hljs-string">"1"</span>,
@<span class="hljs-string">"key2"</span>:@<span class="hljs-string">"2"</span>};
<span class="hljs-built_in">NSLog</span>(@<span class="hljs-string">"%@"</span>,[dic1 objectForKey:@<span class="hljs-string">"key1"</span>]);
<span class="hljs-built_in">NSLog</span>(@<span class="hljs-string">"%@"</span>,[dic1 valueForKey:@<span class="hljs-string">"key2"</span>]);</code>

2.5 allKeys 和 allValues 获得所有的key/value

<code class=" hljs objectivec">    <span class="hljs-built_in">NSDictionary</span> * dic1 = @{@<span class="hljs-string">"key1"</span>:@<span class="hljs-string">"1"</span>,
@<span class="hljs-string">"key2"</span>:@<span class="hljs-string">"2"</span>};
<span class="hljs-built_in">NSArray</span> * keys = [dic1 allKeys];
<span class="hljs-built_in">NSArray</span> * values = [dic1 allValues];</code>

2.6 enumerateKeysAndObjectsUsingBlock 用Block的方式遍历

<code class=" hljs objectivec">这里的stop决定了是否停止遍历。
<span class="hljs-built_in">NSDictionary</span> * dic1 = @{@<span class="hljs-string">"key1"</span>:@<span class="hljs-string">"1"</span>,
@<span class="hljs-string">"key2"</span>:@<span class="hljs-string">"2"</span>};
[dic1 enumerateKeysAndObjectsUsingBlock:^(<span class="hljs-keyword">id</span> key, <span class="hljs-keyword">id</span> obj, <span class="hljs-built_in">BOOL</span> *stop) {
<span class="hljs-built_in">NSLog</span>(@<span class="hljs-string">"%@=>%@"</span>,[key description],[obj description]);
}];</code>

2.7 排序

keysSortedByValueUsingSelector:

keysSortedByValueUsingComparator :

keysSortedByValueWithOptions: usingComparator:

返回Keys的数组，顺序按照value排序顺序。

<code class=" hljs objectivec">  <span class="hljs-built_in">NSDictionary</span> * numsDic = @{@(<span class="hljs-number">2</span>):@<span class="hljs-string">"second"</span>,
@(<span class="hljs-number">1</span>):@<span class="hljs-string">"first"</span>,
@(<span class="hljs-number">3</span>):@<span class="hljs-string">"thrid"</span>};
<span class="hljs-built_in">NSDictionary</span> * strDic = @{@<span class="hljs-string">"id_1"</span>:@<span class="hljs-string">"first"</span>,
@<span class="hljs-string">"id_3"</span>:@<span class="hljs-string">"thrid"</span>,
@<span class="hljs-string">"id_2"</span>:@<span class="hljs-string">"second"</span>};
<span class="hljs-built_in">NSArray</span> * numsSortedKeys = [numsDic keysSortedByValueUsingSelector:<span class="hljs-keyword">@selector</span>(compare:)];
<span class="hljs-built_in">NSArray</span> * strSortedKyes = [strDic keysSortedByValueUsingComparator:^NSComparisonResult(<span class="hljs-keyword">id</span> obj1, <span class="hljs-keyword">id</span> obj2) {
<span class="hljs-built_in">NSString</span> * str1 = obj1;
<span class="hljs-built_in">NSString</span> * str2 = obj2;
<span class="hljs-keyword">return</span> [str1 compare:str2];
}];
<span class="hljs-built_in">NSLog</span>(@<span class="hljs-string">"%@"</span>,numsSortedKeys<span class="hljs-variable">.description</span>);
<span class="hljs-built_in">NSLog</span>(@<span class="hljs-string">"%@"</span>,strSortedKyes<span class="hljs-variable">.description</span>);</code>

输出

2015-02-09 22:04:12.070 DictonaryExample[1037:23292] (

1,

2,

3

)

2015-02-09 22:04:12.070 DictonaryExample[1037:23292] (

“id_1”,

“id_2”,

“id_3”

)

2.8 过滤

keysOfEntriesPassingTest：

返回keys的集合，这些keys符合参数block的约束

<code class=" hljs objectivec">  <span class="hljs-built_in">NSDictionary</span> * numsDic = @{@(<span class="hljs-number">2</span>):@<span class="hljs-string">"second"</span>,
@(<span class="hljs-number">1</span>):@<span class="hljs-string">"first"</span>,
@(<span class="hljs-number">3</span>):@<span class="hljs-string">"thrid"</span>};
NSSet * filteredKyes = [numsDic keysOfEntriesPassingTest:^<span class="hljs-built_in">BOOL</span>(<span class="hljs-keyword">id</span> key, <span class="hljs-keyword">id</span> obj, <span class="hljs-built_in">BOOL</span> *stop) {
<span class="hljs-built_in">BOOL</span> result = <span class="hljs-literal">NO</span>;
<span class="hljs-built_in">NSNumber</span> * numKey = key;
<span class="hljs-keyword">if</span> (numKey<span class="hljs-variable">.integerValue</span> > <span class="hljs-number">2</span>) {
result =  <span class="hljs-literal">YES</span>;
}
<span class="hljs-keyword">return</span> result;
}];
<span class="hljs-built_in">NSLog</span>(@<span class="hljs-string">"%@"</span>,filteredKyes<span class="hljs-variable">.description</span>);</code>

输出

2015-02-09 22:09:50.800 DictonaryExample[1099:25241] {(

3

)}

2.9写到文件

writeToFile:atomically

writeToURL:atomically

<code class=" hljs objectivec">   <span class="hljs-built_in">NSString</span> * path = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, <span class="hljs-literal">YES</span>) firstObject] ;
<span class="hljs-built_in">NSString</span> * fileName = @<span class="hljs-string">"file"</span>;
<span class="hljs-built_in">NSString</span> * filePath = [path stringByAppendingPathComponent:fileName];

<span class="hljs-built_in">NSDictionary</span> * dic = @{@<span class="hljs-string">"key"</span>:@<span class="hljs-string">"value"</span>};
<span class="hljs-built_in">BOOL</span> result = [dic writeToFile:filePath atomically:<span class="hljs-literal">YES</span>];
<span class="hljs-keyword">if</span> (result) {
<span class="hljs-built_in">NSLog</span>(@<span class="hljs-string">"Success"</span>);
}
</code>

2.10Description－常常用来debug输出dictionary的内容。

在之前已经举例好多了，这里不再赘述

三 NSMutableDictionary的额外方法

3.1 添加元素

<code class=" hljs erlang">- <span class="hljs-params">(void)</span>setObject:<span class="hljs-params">(id)</span>anObject
forKey:<span class="hljs-params">(id<<span class="hljs-variable">NSCopying</span>>)</span>aKey
- <span class="hljs-params">(void)</span>setValue:<span class="hljs-params">(id)</span>value
forKey:<span class="hljs-params">(<span class="hljs-variable">NSString</span> *)</span>key
- <span class="hljs-params">(void)</span>setDictionary:<span class="hljs-params">(<span class="hljs-variable">NSDictionary</span> *)</span>otherDictionary</code>

注意，使用KVC的时候，key一定要是NSString。第三个函数是删除之前的元素，然后把otherDictionary元素放到当前dic中。

举例

<code class=" hljs objectivec">    <span class="hljs-built_in">NSMutableDictionary</span> * dic = [[<span class="hljs-built_in">NSMutableDictionary</span> alloc] initWithObjectsAndKeys:@<span class="hljs-string">"object"</span>,@<span class="hljs-string">"key"</span>, <span class="hljs-literal">nil</span>];
<span class="hljs-built_in">NSLog</span>(@<span class="hljs-string">"%@"</span>,dic<span class="hljs-variable">.description</span>);
[dic setDictionary:@{@<span class="hljs-string">"otherKey"</span>:@<span class="hljs-string">"otherValue"</span>}];
<span class="hljs-built_in">NSLog</span>(@<span class="hljs-string">"%@"</span>,dic<span class="hljs-variable">.description</span>);</code>

输出

2015-02-09 22:31:21.417 DictonaryExample[1232:31666] {

key = object;

}

2015-02-09 22:31:21.418 DictonaryExample[1232:31666] {

otherKey = otherValue;

}

3.2删除元素

<code class=" hljs erlang">- <span class="hljs-params">(void)</span>removeObjectForKey:<span class="hljs-params">(id)</span>aKey
- <span class="hljs-params">(void)</span>removeAllObjects
- <span class="hljs-params">(void)</span>removeObjectsForKeys:<span class="hljs-params">(<span class="hljs-variable">NSArray</span> *)</span>keyArray</code>

比较容易忽视的是第三个，删除一组key。

举例

<code class=" hljs lua"> NSDictionary * dic = @{@(<span class="hljs-number">1</span>):@<span class="hljs-string">"first"</span>,
@(<span class="hljs-number">2</span>):@<span class="hljs-string">"second"</span>,
@(<span class="hljs-number">3</span>):@<span class="hljs-string">"thrid"</span>};
NSMutableDictionary * mutableDic = <span class="hljs-string">[[NSMutableDictionary alloc] initWithDictionary:dic];
[mutableDic removeObjectsForKeys:@[@(1),@(2)]]</span>;
NSLog(@<span class="hljs-string">"%@"</span>,mutableDic.description);</code>

输出

<code class=" hljs fix"><span class="hljs-attribute">2015-02-09 22:34:13.112 DictonaryExample[1273:32793] {
3 </span>=<span class="hljs-string"> thrid;
}</span></code>