問題：安裝cocoapods 報SSL證書的問題，如下錯誤

ERROR: SSL verification error at depth 2: self-signed certificate in certificate chain (19)

ERROR: Root certificate is not trusted (/C=GB/ST=Greater Manchester/L=Salford/O=Comodo CA Limited/CN=AAA Certificate Services)

ERROR: SSL verification error at depth 2: self-signed certificate in certificate chain (19)

ERROR: Root certificate is not trusted (/C=US/O=DigiCert Inc/OU=www.digicert.com/CN=DigiCert Global Root CA)

Successfully installed cocoapods-1.11.2

Parsing documentation for cocoapods-1.11.2

Done installing documentation for cocoapods after 1 seconds

1 gem installed

[!] Couldn't determine repo type for URL: `https://cdn.cocoapods.org/`: SSL_connect returned=1 errno=0 peeraddr=172.67.74.167:443 state=error: certificate verify failed (unable to get local issuer certificate)

解決方案：

1.下載證書

可以使用 wget 下載或者直接在網頁下載

https://curl.se/ca/cacert.pem

2.設置環境變量

vim /etc/profile  

# System-wide .profile for sh(1)

if [ -x /usr/libexec/path_helper ]; then
        eval `/usr/libexec/path_helper -s`
fi

if [ "${BASH-no}" != "no" ]; then
        [ -r /etc/bashrc ] && . /etc/bashrc
fi
# 設置環境變量的路徑，/root/cacert.pem為下載證書后放的位置
export SSL_CERT_FILE=/root/cacert.pem

source /etc/profile 

3.安裝cocoapods，指定版本1.11.2

sudo gem install -n /usr/local/bin cocoapods -v 1.11.2 

注釋：使用gem安裝問題有點小多，如果不需要指定版本可以選擇brew安裝最新的版本。終端輸入 ： brew install cocoapods 即可