常见集合

vector:
允许我们一个挨着一个地储存一系列数量可变的值 字符串(string)是一个字符的集合
String 类型，不过在本章我们将深 入了解
哈希 map(hash map):
允许我们将值与一个特定的键(key)相关联。这是一个叫做 map 的更通用的数据结构的特定实现。

vector

for (index,container) in self.containers.iter().enumerate() {
            for (i, conf) in container
                .config
                .clone()
                .unwrap_or_else(|| vec![])
                .iter()
                .enumerate()
            {
                let mut values = BTreeMap::new();
                //config name is file path
                let filename = Path::new(conf.path.as_str())
                    .file_name()
                    .unwrap()
                    .to_os_string()
                    .into_string()
                    .expect("config file name");
                values.insert(filename, conf.resolve_value(resolved_vals.clone()));
                // make sure configmap name global unique in the namespace
                // multiply containers in one component and multiply configmap in on container
                // configmap name: instance_name + "-" + contrainer_index + "-" + config index
                let config_map_name = utils::concat_str(instance_name.clone(),index.to_string(),i.to_string());
                configs.insert(config_map_name.clone(), values);
            }
        }

# create new vector
let v: Vec<i32> = Vec::new();

# create and initial
let v = vec![1, 2, 3];

# add new item
let mut v = Vec::new();
v.push(5);
v.push(6); 
v.push(7); 
v.push(8);

# read
let v = vec![1, 2, 3, 4, 5];
let third: &i32 = &v[2];
println!("The third element is {}", third);
match v.get(2) {
      Some(third) => println!("The third element is {}", third), 
      None => println!("There is no third element."),
}

遍历

let v = vec![100, 32, 57];
for i in &v {
    println!("{}", i);
}

遍历2

# 给每个元素+50
let mut v = vec![100, 32, 57];
for i in &mut v {
    *i += 50; 
}

遍历

let v = vec!['a', 'b', 'c'];
for (index, value) in v.iter().enumerate() { 
         println!("{} is at index {}", 
         value, index);
}

使用枚举来储存多种类型

enum SpreadsheetCell {
    Int(i32),
Float(f64),
    Text(String),
}
let row = vec![
     SpreadsheetCell::Int(3), 
     SpreadsheetCell::Text(String::from("blue")), 
     SpreadsheetCell::Float(10.12),
];

string

let mut s = String::new();
let data = "initial contents"; let s = data.to_string();
// 该方法也可直接用于字符串字面值:
let s = "initial contents".to_string();

# 可以通过 push_str 方法来附加字符串 slice，从而使 String 变长
let mut s = String::from("foo"); 
s.push_str("bar");

---

let s1 = String::from("Hello, ");
let s2 = String::from("world!");
let s3 = s1 + &s2; // 注意 s1 被移动了，不能继续使用

这个语句会获 取 s1 的所有权，附加上从 s2 中拷贝的内容，并返回结果的所有权赋给s3
所以执行完, s1失效, s2和s3继续使用

let s1 = String::from("tic");
let s2 = String::from("tac");
let s3 = String::from("toe");
let s = s1 + "-" + &s2 + "-" + &s3;

# 等同
let s1 = String::from("tic");
let s2 = String::from("tac");
let s3 = String::from("toe");
let s = format!("{}-{}-{}", s1, s2, s3);

长度

 let len = String::from("Hola").len();

HashMap

use std::collections::HashMap;
let mut scores = HashMap::new();

scores.insert(String::from("Blue"), 10); 
scores.insert(String::from("Yellow"), 50);

访问

use std::collections::HashMap;
let mut scores = HashMap::new();

scores.insert(String::from("Blue"), 10); 
scores.insert(String::from("Yellow"), 50);

let team_name = String::from("Blue"); 
let score = scores.get(&team_name);

遍历

use std::collections::HashMap;
let mut scores = HashMap::new();
scores.insert(String::from("Blue"), 10); scores.insert(String::from("Yellow"), 50);
for (key, value) in &scores {
    println!("{}: {}", key, value);
}

检查key是否存在

use std::collections::HashMap;
let mut scores = HashMap::new();
scores.insert(String::from("Blue"), 10); 
scores.entry(String::from("Yellow")).or_insert(50);
scores.entry(String::from("Blue")).or_insert(50); println!("{:?}", scores);

根据已存在值更新

use std::collections::HashMap;
let text = "hello world wonderful world";
let mut map = HashMap::new();
for word in text.split_whitespace() {
       let count = map.entry(word).or_insert(0);
       *count += 1;
}
println!("{:?}", map);