1. Introduction
In programming, it is a common task to determine whether two objects are equal. It is very important to determine whether objects are equal in many cases, such as:
- Unit Testing: When writing unit tests, it is often necessary to verify whether the output of the function meets expectations, which involves whether the comparison objects are equal.
-
Data structure operation: In use
mapWhen a data structure is used, it may be necessary to determine whether the two objects are equal to perform operations such as element search, deletion or update. - Cache Management: When using a cache system, it is necessary to compare whether the data stored in the cache is equal to the expected value to ensure the consistency and correctness of the cache.
Therefore, it is very common to determine whether objects are equal in actual development and has a wide range of application scenarios. In Go, for different types of objects, there are different ways to determine whether they are equal. Understanding and mastering these methods is very important for writing high-quality code. In the following content, we will introduce in detail the methods and techniques of how to judge whether objects are equal in Go language.
2. Basic instructions
When comparing whether the objects are equal, we need to choose the appropriate method according to the specific situation. For basic types, use==Operators can get the correct result. For custom types, we need to define the rules of equality by ourselves, and we usually compare them by implementing the corresponding methods. In addition, when relatively complex data structures or reference types, special attention should be paid to the judgment of equality to avoid unexpected results.
It is worth noting that equality comparisons in Go are also limited by data types. For example, slices, maps, and function types are incomparable because they cannot directly compare values. When comparing custom structures containing these types, you need to pay attention to using other methods to determine the value equality.
In the following content, we will explore in-depth methods and techniques for judging whether objects are equal in Go, and help you correctly handle object equality comparison in actual development.
3. Comparison of Equalities of Basic Types
In Go, use==Operators can compare equality of basic types. Basic types include integers, floating point numbers, boolean values, and strings. Here is how to use it==An introduction to operator comparison of basic types equality.
For integer equality comparison,int、int8、int16、int32、int64etc. You can use it directly==Operators are compared. For example:a == b,ifaandbThe value of the expression is equal, then the result of the expression istrue, otherwisefalse. Here is a simple code:
a := 10
b := 20
if a == b {
("a and b are equal")
} else {
("a and b are not equal")
}For floating point equality comparison, due to floating point number types (e.g.float32andfloat64) There are accuracy limitations, so use it directly==Comparison of operators may be inaccurate, and it is recommended to use floating point comparison functions (such asCombined with a small error range) to determine the equality of floating point numbers. For example:(a - b) < epsilon,inepsilonis a small error range, if the absolute value of the difference between two floating point numbers is less thanepsilon, they are considered equal. Here is a simple code:
x := 3.14
y := 2.71
if (x - y) < 0.0001 {
("x and y are equal")
} else {
("x and y are not equal")
}For Boolean equality comparison, there are only two possible values for Boolean type:trueandfalse. Can be used directly==Operators compare the equality of two boolean values. For example:a == b,ifaandbThe value of equality istrue, otherwisefalse。
p := true
q := false
if p == q {
("p and q are equal")
} else {
("p and q are not equal")
}For string equality comparison, you can use it directly==Operators compare the equality of two characters. For example:a == b,ifaandbRepresents the same string, the result istrue, otherwisefalse。
str1 := "hello"
str2 := "hello"
if str1 == str2 {
("str1 and str2 are equal")
} else {
("str1 and str2 are not equal")
}In the above example, by using the equality operator==To compare the equality of the basic data types of different types, if the two values are equal, the corresponding logic is executed. If not equal, other logic is executed. The equality of this basic type is quite concise and intuitive.
4. Comparison of equality of custom types
4.1 Only basic type fields can be compared with the == operator?
If the custom type only has a basic type, you can use it directly==Operators to implement custom types comparisons.==The operator will traverse each field of the custom type to judge the equality of the field values. Here is a simple code:
import (
"fmt"
"reflect"
)
type Person struct {
Name string
Age int
}
func main() {
p1 := Person{Name: "Alice", Age: 25}
p2 := Person{Name: "Alice", Age: 25}
equal := p1 == p2
if equal {
("Two objects are equal")
} else {
("Two objects are not equal")
}
}
We definedPersonStructure, there are two basic types of fields in the structure. In the example above, we created twoPersonStructural objectp1andp2, their field values are exactly the same. Then pass==Operator, we can determine whether these two objects are equal, and the result is as follows:
Two objects are equal
Therefore, if all fields in the custom structure have the basic types, you can use it==operators to compare.
4.2 Can I compare the reference type with the == runner?
Let's try it below. If there is a field of pointer type in the custom structure, then use it==Comparison of operators and whether they can be compared correctly, the following is a simple code:
type Person struct {
Name string
Age int
address *Address
}
type Address struct {
city string
}
func main() {
p1 := Person{Name: "Alice", Age: 30, address: &Address{city: "beijing"}}
p2 := Person{Name: "Alice", Age: 30, address: &Address{city: "beijing"}}
equal := p1 == p2
if equal {
("Two objects are equal")
} else {
("Two objects are not equal")
}
}
Here we definePersonIn the structure, there is a field of pointer typeaddress. We create two objectsp1andp2, the field values of each field are the same here, and the return values of the two objects expected to be the same. But its output is:
Two objects are not equal
What's the reason here? Actually==Operators do not compare their contents for pointer types, but rather their reference addresses. Therefore, even if the contents of the two reference types are the same and the memory addresses they point to are different, they are still considered unequal. herep1andp2Of two objectsaddressThe object pointed to by the field is not the same, and it is used at this time==Comparing whether the objects are equal will return False, which is not as expected at this time. Secondly, if the structure contains a slice or map type field, it is not allowed to use it directly at this time.==Operator, the direct compilation failed. Therefore, if there is a reference type field in the custom structure, it cannot be used at this time==Let's compare.
4.3 If you include a reference type field, how to compare whether two objects are equal?
If there is a reference type in the structure, here are two ways to compare the equality of the object. One is to implement customizationEqualsMethod to implement; the second is to use()Functions to compare whether objects are equal. Here we show how to implement customizationEqualsThe method is used to determine whether the objects are equal. The code example is as follows:
type Person struct {
Name string
Age int
Colors []string
}
func (p Person) Equals(other Person) bool {
if != || != || len() != len() {
return false
}
for i := range {
if [i] != [i] {
return false
}
}
return true
}
func main() {
p1 := Person{Name: "Alice", Age: 30, Colors: []string{"Red", "Green", "Blue"}}
p2 := Person{Name: "Bob", Age: 25, Colors: []string{"Red", "Green", "Blue"}}
((p2)) // Output true}
In the above example, wePersonThe structure has been implementedEqualsMethod to compare objects equality. In this method, we first compareNameandAgeAre the fields equal and then slice them one by oneColorsWhether the elements of ? We only consider two objects equal when all fields are equal.
Through customEqualsMethod, you can compare whether objects containing reference types fields such as slices are equal according to your own needs. Please note that the equality comparison here is determined based on the rules you define and needs to be modified appropriately according to the specific circumstances.
If you think custom implementationEqualThe method is quite troublesome, there is a standard libraryreflectPackage providedDeepEqualFunctions, which can be used to compare the depth of two objects whether they are equal.DeepEqualFunctions can compare multiple types including basic types, slices, maps, structures, etc. Can be called directlyDeepEqualTo achieve a deep-level comparison of complex structures, the examples are as follows:
type Person struct {
Name string
Age int
Colors []string
}
func main() {
p1 := Person{Name: "Alice", Age: 30, Colors: []string{"Red", "Green", "Blue"}}
p2 := Person{Name: "Bob", Age: 25, Colors: []string{"Red", "Green", "Blue"}}
// Use the DeepEqual function to compare whether two objects are equal equal := (p1, p2)
(equal) // Output: true}In the above example, we define aPersonStructure and two objects are createdp1、p2. Then, we useFunctions are compared separatelyp1andp2Whether the objects are equal. Finally, by printing the results we can see the results of the equality comparison.
4.4 Comparison of custom Equals methods and DeepEqual
For customizationEqualsMethod, you can define aEqualsMethod, which accepts another object of the same type as a parameter and compares whether the fields of the object are equal according to its own logic. This approach requires manually comparing each field and considering how fields of reference type are handled.
Functions are a function provided in the Go standard library, which can recursively compare whether two objects are equal. It compares the object's types and values and recursively compares the object's fields when needed. It should be noted thatFunction use needs to be introducedreflectpackage, and deep traversal is performed when comparing objects, so there may be some performance overhead. Additionally, this function may have unexpected results when comparing certain types, so be especially careful when using it.
To sum up, you can choose a suitable method according to your needs to compare the equality of objects containing reference types in a custom structure. CustomizeEqualThe method provides a more flexible way to customize based on specific field comparison logic, andFunctions provide a convenient way to compare recursively, but require careful use in performance and in some special cases.
5. Summary
This article introduces methods and techniques to determine whether objects are equal in Go language. Depending on the type and field of the object, we can use different methods to compare equality.
For basic types, you can use them directly==Operators are compared. For example, basic types such as integers, floating point numbers, boolean values, and strings can be used==Operators determine equality.
For custom types, if only the basic type fields are included, you can directly pass==Operators to implement comparison. However, if the reference type field is included, it cannot be used at this time==To achieve comparison, you can choose to implement custom onesEqualsMethod to make in-depth comparisons, or useFunctions are compared.
In actual development, appropriate comparison methods are selected according to needs to ensure that the equality of objects is in line with expectations. In addition, you need to pay attention to the handling of non-comparable types (such as slices, maps, and function types) to avoid unexpected results.
Understanding and mastering the methods of comparing object equality is very important for writing high-quality code. By correctly judging the equality of objects, the correctness and consistency of the program can be ensured.
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